Countries Involved in World War 1 (WWI)

Country	World War I Alignment↓	Role/Level of Involvement in WWI	Year Entered WWI	Region	Additional WWI Details
Guatemala	none / Allies	Minor	1918	North America	Guatemala remained noncommittal through most of WWI. Guatemala's actual participation in WWI was minimal, though it did declare war on Germany on April 21 (some sources say April 23), 1918.
Haiti	none / Allies	Minor	1918	North America	The US sent troops to occupy Haiti starting in July 1915, before the US had even entered the war, in order to protect US interests in the country, where insurgents had just violently deposed a dictatorial ruler. After remaining noncommittal through most of WWI, Haiti's Council of State declared war on Germany in July 1918, largely in response to German u-boat activity and the sinking of a French ship whose crew and passengers included Haitian citizens.
Honduras	none / Allies	Minor	1918	North America	Honduras remained noncommittal through most of WWI. The country's actual participation in WWI was minimal, though it did declare war on Germany on July 19, 1918.
Cuba	none / Allies	Minor	1917	North America	Cuba spent much of WWI as a noncommittal (undeclared neutral) country, but officially joined the Allies in April 1917, one day after the United States joined the Allies. 25,000 Cuban soldiers were reportedly drafted, with plans to join the Allies in France. However, only 100 medical personnel made the trip before the armistice was enacted.
Nicaragua	none / Allies	Minor	1918	North America	As with many South American and Central American countries, Nicaragua's actual participation in WWI was minimal. It did, however, sever ties with the Central Powers in April 1917 and declare war on Germany in April 1918.
Costa Rica	none / Allies	Minor	1918		Costa Rica severed relations with Germany on Sept. 21, 1917 and declared war on May 23, 1918 (some sources say May 24). Costa Rica did not deploy troops or supplies to the Allies, though a handful of Costa Ricans are known to have independently joined the French Foreign Legion.
Panama	none / Allies	Minor	1917	North America	Panama remained noncommittal through most of WWI, but eventually declared war on Germany on 7 April 1917, one day after the US entered the war. While only a handful of Panamanians saw combat (typically as part of US forces), the country's citizens supported the Allies in various other ways, such as purchasing Freedom Bonds and detaining a number of Germans suspected of possible espionage involving the Panama Canal.
Colombia	none	none	none	South America	Although it never formally declared its neutrality, Colombia remained noncommittal throughout WWI.
Sudan	none	Minor	1914	Africa	Modern-day Sudan consists largely of portions of regions that were British-controlled Anglo-Egyptian Sudan and French-controlled French Sudan at the time of WWI. Moreover, the Sudanese often resisted their European overseers to the point of rebellion. As such, while Sudan arguably entered the war along with France and Great Britain in August 1914, it would be a miscategorization to state that Sudan was part of the Allies.
Peru	none	Minor	none	South America	Peru's involvement in WWI was minimal, though the country did sever diplomatic relations with the Central Powers in October 1917.
Chile	none	none	none	South America	Although it never formally declared its neutrality, Chile remained noncommittal throughout WWI.
Ecuador	none	Minor	none	South America	Ecuador's involvement in WWI was minimal. Ecuador maintained a position of unofficial neutrality, though it did sever diplomatic relations with the Central Powers in December 1917.
Bolivia	none	Minor	none	South America	Bolivia's involvement in WWI was minimal, though the country did sever diplomatic relations with the Central Powers in April 1917.
South Sudan	none	Minor	1914	Africa	Modern-day South Sudan consists largely of portions of regions that were British-controlled Anglo-Egyptian Sudan and French-controlled French Sudan at the time of WWI. Moreover, the Sudanese often resisted their European overseers to the point of rebellion. As such, while South Sudan arguably entered the war along with France and Great Britain in August 1914, it would be a miscategorization to state that Sudan was part of the Allies.
Dominican Republic	none	Minor	1916	North America	The Dominican Republic's involvement in WWI was minimal, though the country did sever diplomatic relations with the Central Powers. Also, the United States preemptively occupied the DR from 1916 to 1924 out of fears that Germany would do the same. The occupation was unpopular in both the US and the DR.
Paraguay	none	none	none	South America	Although it never formally declared its neutrality, Paraguay remained noncommittal throughout WWI.
Uruguay	none	Minor	none	South America	Uruguay's involvement in WWI was minimal, though the country did sever diplomatic relations with the Central Powers in October 1917.
Moldova	none	Minor	1914	Europe	A territory of Russia leading up to World War I, Moldova rebelled during the war and declared independence as the Moldavian Democratic Republic in December 1917. It would later re-merge with Romania (with which it had also merged in the 1800s before being conquered by Russia), find itself absorbed into the USSR, and declare its independence again in 1991.
Albania	none	Secondary	1914	Europe	Having just attained its independence in 1912, the Principality of Albania's newly established government disintegrated at the start of WWI without formally declaring allegiance to either side. During the war, parts of Albania were invaded and occupied at various times by armies from Greece, Italy, Serbia and Montenegro, Germany, Austria-Hungary, and Bulgaria. Albanians suffered heavy casualties due to the actions of both Central and Allied forces. Allied forces drove out the occupiers for good in 1918, and Albania was recognized as a sovereign state in 1920.
Bahrain	none	Minor	none	Asia	Bahrain was a British protectorate during World War I. However, the Bahraini people were often less than enthusiastic about the arrangement and were largely unsympathetic to the Allies' cause. Most of the attention paid Bahrain in WWI consisted of fending off attempts by neighboring countries to occupy and annex the country.
United States	Neutral / Allies	Principal	1917		The United States initial maintained a stance of neutrality (though US banks had given substantial loans to Great Britain and France). However, reports of German atrocities in Belgium, as well as Germany's sinking of the passenger ship Lusitania with 128 Americans aboard began tilting public perceptions against Germany. In early 1917, Germany sank several US merchant ships and sent a telegram, intercepted by British intelligence, in which Germany urged Mexico to attack the US. In response, the US declared war on the German Empire in April 1917 and began assisting the Allies with food, supplies, munitions, and troops. By the summer of 1918, approximately two million US soldiers had landed in France to join the fray.
Brazil	Neutral / Allies	Minor	1917	South America	Mired in internal politics, Brazil remained neutral for much of the war, but joined the Allies in October 1917 and contributed medical staff, military officers, aviators, and naval support.
Philippines	Neutral / Allies	Minor	1917	Asia	The Philippines was a semi-autonomous US colony during WWI, and the 1916 Jones Act (Philippine Autonomy Act) formally established the country's path to independence. The Philippine National Guard was established with the intent of joining existing Allied forces in Europe, but the war ended before the merger could occur.
Thailand	Neutral / Allies	Secondary	1917	Asia	Siam (now Thailand) initially declared itself neutral in 1914, but declared war on the Central Powers in 1917, following the United States' entry into the war. Siamese troops fought in Europe.
Italy	Neutral / Allies	Principal	1915	Europe	At the start of WWI, Italy was part of the Triple Alliance with Germany and Austria-Hungary. Italy initially remained neutral despite strong sentiment to side against its then-ally, but historical enemy, Austria-Hungary. During secret negotiations in early 1915, Great Britain and France promised to support Italy's annexation of territory along the Austria-Hungarian border. Italy resigned from the Triple Alliance on May 03, 1915 and declared war against Austria-Hungary at midnight on May 23, 1915, thereby joining the Allies. At the start of the war, the Italian army boasted fewer than 300,000 men, but swelled to more than 5 million by the war’s end in November 1918. Approximately 460,000 Italian soldiers were killed and 955,000 wounded in the conflict.
Belgium	Neutral / Allies	Secondary	1914	Europe	Belgium attempted to remain neutral in observance of the 1839 Treaty of London, but was invaded and occupied by Germany on Aug. 04, 1914. German forces engaged in significant atrocities against the Belgian population in what came to be known as "the Rape of Belgium". A resistance movement quickly emerged to fight the German occupiers, and Allied and Belgian armies eventually liberated the country. Over the course of the war, Belgium's government lived in exile, as did eight percent of its citizens.
Portugal	Neutral / Allies	Secondary	1916	Europe	Portugal initially adopted a neutral stance in World War I, but eventually joined the Allies on March 9, 1916 after Germany declared war on Portugal. Portuguese colonies in Africa had already been fighting German forces for some time.
Greece	Neutral / Allies	Secondary	1917	Europe	Greece initially held a neutral stance during WWI. The Greek Prime Minister supported the Allies, while King Constantine I (who had ties to Germany) wished to remain neutral. This disagreement eventually led to the establishment of the Provisional Government of National Defence / State of Thessaloniki, an alternate government which established an "Army of National Defence" and joined the Allies in late 1916. The provisional government eventually replaced the previous government and Greece joined the Allies properly in 1917.
Luxembourg	Neutral / Allies	Minor	1914	Europe	Declared a neutral nation in the 1867 Treaty of London, Luxembourg attempted to remain neutral during WWI, but was invaded and occupied by Germany. While Luxembourg's government maintained its policy of neutrality, approximately 1,000 private citizens joined the French army.
Tonga	Neutral / Allies	Minor	1914	Oceania	Tonga initially declared neutrality, as it enjoyed strong relations with both Great Britain (with which it has a protection agreement) and Germany. Although Tonga never officially renounced its neutrality, it did eventually assist the Allies by allowing the British to incarcerate or restrict Germans living in Tonga and by contributing 90+ troops to the New Zealand Expeditionary Force (NZEF).
Indonesia	Neutral	Minor	none	Asia	Alternately known as the Dutch East Indies, Indonesia spent WWI as a colony of the Kingdom of the Netherlands, which remained neutral during the war. Although many Indonesians were sympathetic to the Central Powers (feeling a particular kinship to fellow Muslims in the Ottoman Empire), Indonesia remained neutral and largely uninvolved in the war.
Ethiopia	Neutral	Minor	none	Africa	Alternately known as Abyssinia at the time, Ethiopia never formally declared its neutrality, but spent WWI being courted by both the Allies and the Central Powers. A coup in 1916 seemed designed to tilt the country toward the Allies, but no allegiance was declared. In fact, the government prevented its civilians from being recruited into the Allied forces in 1917.
Mexico	Neutral	none	none	North America	Mexico remained neutral throughout WWI.
Spain	Neutral	Secondary	none	Europe	Declared neutrality on Aug. 4, 1914. During 1914 Battle of Rio de Oro, Spanish Guinea provided sanctuary for German soldiers and refugees from Kamerun (Cameroon).
Argentina	Neutral	none	none	South America	Argentina remained neutral throughout WWI.
Venezuela	Neutral	none	none	South America	Venezuela remained neutral throughout WWI.
Netherlands	Neutral	Secondary	none	Europe	Declared neutrality on July 30, 1914. Provided humanitarian aid.
Sweden	Neutral	Secondary	1914	Europe	Declared neutrality on Aug. 3, 1914. Provided humanitarian aid.
Switzerland	Neutral	Secondary	1914	Europe	Declared neutrality on Aug. 2, 1914. Provided humanitarian aid.
El Salvador	Neutral	none	none	North America	El Salvador remained neutral throughout World War I.
Norway	Neutral	Secondary	1914	Europe	Declared neutrality on Aug. 4, 1914. Provided humanitarian aid.
Equatorial Guinea	Neutral	Minor	none	Africa	Equatorial Guinea spent WWI as a colony of Spain, which remained neutral. However, it did provide sanctuary for German soldiers and refugees from Kamerun (Cameroon).
Western Sahara	Neutral	Minor	none		At the time of WWI, Rio de Oro/Spanish Sahara was a colony of Spain, which remained neutral during the war. However, its shore was the site of the August 1914 Battle of Rio de Oro between British and German naval forces.
Iceland	Neutral	Minor	none	Europe	Part of the Kingdom of Denmark until 1918; remained neutral.
Andorra	Neutral	Minor	none	Europe	Andorra remained neutral throughout World War I. Reports surfaced in 1958 that the country had declared war on Germany in 1914 and hadn't signed a peace treaty until 1958, but those reports lack actual documentation.
Greenland	Neutral	Minor	none		Part of the Kingdom of Denmark, which was neutral during the war.
San Marino	Neutral	Minor	none	Europe	Despite propaganda erroneously articles claiming San Marino had declared war on Austria-Hungary, San Marino remained neutral in WWI. However, a small number of Sammarinese volunteers did join the Italian army and serve on the Allied side.
Tanzania	Mixed	Secondary	1914	Africa	Modern Tanzania spent WWI split between Tanganyika (British colony) and German East Africa (German colony), both of which joined the war in 1914.
Yemen	Mixed	Secondary	1914	Asia	During WWI, the area that is now Yemen was split. The port city/region of Aden was an important British colony, and sided with the Allies. Another region was part of the Ottoman Empire, a principal Central Power that entered the war in July 1914 and which also included all of modern Israel, Lebanon, and Turkey, as well as parts of Iraq, Jordan, Saudi Arabia, and Syria. Part of this occupied region broke away from the Ottomans in 1916 and established the Kingdom of Hejaz (with British support) and also fought alongside the allies.
Ukraine	Mixed	Principal	1914	Europe	Modern-day Ukraine was not a sovereign state at the time of WWI, and instead had territory in both Russia and Austria-Hungary. Thus, Ukrainian soldiers fought for both the Allied and Central Powers, with approximately 4.5 million in the Russian military and between 250,000-300,000 in the Austro-Hungarian military.
Poland	Mixed	Secondary	1914	Europe	At the time of WWI, modern-day Poland consisted of three territories, ruled by Austria-Hungary, Germany and Russia. As a result, Poles served in the armies of both the Allies and the Central Powers. More than 3.5 million Polish soldiers fought for one side or the other. As a result, much of the country was occupied at one time or another. Poland declared independence as the Republic of Poland in November 1918.
Ghana	Mixed	Minor	1914	Africa	Modern-day Ghana spent WWI split between the British Gold Coast—a British colony aligned with the Allies—and Togoland, a German colony that also included modern Togo and aligned with the Central Powers.
Czech Republic	Mixed	Secondary	1918	Europe	The country now known as the Czech Republic was part of Austria-Hungary during WWI, and so aligned with the Central Powers. However, the citizenry was not unanimous in its support. The Czechoslovak Legion was a volunteer fighting force, made up of more than 100,000 citizens of the modern-day Czech Republic and Slovakia, who fought alongside the Allies in WWI. The Czech Republic declared independence from Austria-Hungary in October 1918 (as Czechoslovakia).
Togo	Mixed	Secondary	1914	Africa	Then known as Togoland, modern Togo began WWI as a protectorate of Germany, which entered the war as a Central Power on Aug. 1, 1914. Togoland was taken by British/French forces in 1914 and became a divided French/UK colony (French Togoland / British Togoland).
Libya	Mixed	Secondary	1915	Africa	At the time of WWI, modern-day Libya was technically an Italian colony, having been ceded from the Ottoman Empire to Italy in 1912. Therefore, it joined the Allies along with Italy in declared war against Germany on May 23, 1915. However, the Senussi, a Muslim order with significant power in the region, opposed Italian rule and fought against the Allies, particularly Italy and Great Britain.
Slovakia	Mixed	Principal	1914	Europe	Slovakia spent WWI as a territory of Austria-Hungary, which triggered WWI with its declaration or war against Serbia on July 28, 1914. As such, thousands of Slovakians served in the Hungarian military. However, many others secretly joined the Czechoslovak Legion, a a volunteer fighting force made up of more than 100,000 citizens of the modern-day Czech Republic and Slovakia, and fought alongside the Allies in WWI. Slovakia declared independence from Austria-Hungary in October 1918 (as Czechoslovakia).
Georgia	Mixed	Secondary	1914	Asia	Modern Georgia began WWI as part of the Russian Empire, a major Allied participant. However, Georgia declared its independence following the Russian Revolution of 1917 and became a German protectorate for a time. After the war, Georgia was occupied by the British, granted full independence, and then annexed by the USSR in 1922 until it regained its independence in 1991.
Turkey	Central Powers	Secondary	1914	Asia	In 1914, modern-day Turkey was the headquarters of the Ottoman Empire/Turkish Empire (Anatolia), a principal Central Power that entered the war in July 1914 and which also included all of modern Israel and Lebanon, as well as parts of Iraq, Jordan, Saudi Arabia, Syria, and Yemen. Ottoman forces aligned with the Central Powers and fought against a wide range of Allied forces, including Brits, Greeks, Jews, French, Russians, and other arabs who had chosen the Allied side.
Germany	Central Powers	Principal	1914	Europe	Aligned with Austria-Hungary, Germany was a principal Central Power and declared war against Russia on Aug. 01, 1914. Germany fought on multiple fronts, and by the time the war ended, more than 1.7 million German soldiers and 430,000 German civilians had died. The German monarchy was overthrown near the end of the war.
Iraq	Central Powers	Principal	1914	Asia	In 1914, much of modern-day Iraq was part of the Ottoman Empire/Turkish Empire, a principal Central Power that entered the war in July 1914 and which also included all of modern Israel, Lebanon, and Turkey, as well as parts of Jordan, Saudi Arabia, Syria, and Yemen. Ottoman forces aligned with the Central Powers and fought against a wide range of Allied forces, including Brits, Greeks, Jews, French, Russians, and other arabs who had chosen the Allied side.
Cameroon	Central Powers	Secondary	1914	Africa	Modern Cameroon was a colony of Germany during WWI and so entered the war by association. Then known as Kamerun, Cameroon was the site of the August 1914 - March 1916 Kamerun Campaign. Kamerun was invaded by the British and French over the course of the war, as German forces were stationed there.
Syria	Central Powers	Principal	1914	Asia	In 1914, much of modern-day Syria was part of the Ottoman Empire/Turkish Empire (Anatolia), a principal Central Power that entered the war in July 1914 and which also included all of modern Israel, Lebanon, and Turkey, as well as parts of Iraq, Jordan, Saudi Arabia, and Yemen. Ottoman forces aligned with the Central Powers and fought against a wide range of Allied forces, including Brits, Greeks, Jews, French, Russians, and other arabs who had chosen the Allied side. Some sources indicate that Syria experienced higher deaths as a proportion of the total population than any other country during WWI.
Rwanda	Central Powers	Minor	1914	Africa	Rwanda (Ruanda/German East Africa) was a colony of Germany, which entered the war as a Central Power on Aug. 1, 1914. It was invaded and controlled by Belgian forces.
Burundi	Central Powers	Minor	1914	Africa	Burundi was a German colony (German East Africa) at the start of the war, and so entered the war by association. Burundi men of fighting age were conscripted into the German East Africa Army, commanded by General Paul von Lettow-Vorbeck, who refused to surrender to the Allies until Nov. 25, 1918 despite the fact that Belgian forces had taken control of the country.
Jordan	Central Powers	Principal	1914	Asia	In 1914, much of modern-day Jordan was part of the Ottoman Empire/Turkish Empire, a principal Central Power that entered the war in July 1914 and which also included all of modern Israel, Lebanon, and Turkey, as well as parts of Iraq, Saudi Arabia, Syria, and Yemen. Ottoman forces aligned with the Central Powers and fought against a wide range of Allied forces, including Brits, Greeks, Jews, French, Russians, and other arabs who had chosen the Allied side.
Papua New Guinea	Central Powers	Minor	1914	Oceania	Papua New Guinea began WWI as a colony of Germany, which entered the war on Aug. 1, 1914. Australia captured and occupied Papua New Guinea in 1914 and held it the remainder of the war.
Hungary	Central Powers	Principal	1914	Europe	Half of the Austro-Hungarian Empire's dual monarchy. Its heir, Archduke Franz Ferdinand, was assassinated in Sarajevo on June 28, 1914; Austria-Hungary was the first nation to declare war (on Serbia on July 28, 1914).
Israel	Central Powers	Principal	1914	Asia	In 1914, modern-day Israel was part of the Ottoman Empire/Turkish Empire (Anatolia), a principal Central Power that entered the war in July 1914 and which also included all of modern Lebanon, and Turkey, as well as parts of Iraq, Jordan, Saudi Arabia, Syria, and Yemen. Ottoman forces aligned with the Central Powers and fought against a wide range of Allied forces, including Brits, Greeks, Jews, French, Russians, and other arabs who had chosen the Allied side.
Austria	Central Powers	Principal	1914	Europe	Austria was part of Austria-Hungary during WWI. Its heir, Archduke Franz Ferdinand, was assassinated in Sarajevo on June 28, 1914. Austria-Hungary was the first nation to declare war (on Serbia on July 28, 1914) in World War I.
Bulgaria	Central Powers	Principal	1915	Europe	Having established its independence from the Ottoman Empire in 1908, Bulgaria declared entry into the war as a Central Power on Oct. 11, 1915. While it was approached to join the Allies, it agreed to side with the Central Powers after being promised Macedonia, which was then part of Serbia.
Lebanon	Central Powers	Principal	1914	Asia	In 1914, modern-day Lebanon was a semi-autonomous part of the Ottoman Empire/Turkish Empire, a principal Central Power that entered the war in July 1914 and which also included all of modern Israel and Turkey, as well as parts of Iraq, Jordan, Saudi Arabia, Syria, and Yemen. Ottoman forces aligned with the Central Powers and fought against a wide range of Allied forces, including Brits, Greeks, Jews, French, Russians, and other arabs who had chosen the Allied side. Starvation became a major concern in Lebanon during the war.
Croatia	Central Powers	Principal	1914	Europe	Croatia spent WWI as part of the Triune Kingdom of Croatia, Slavonia and Dalmatia, a territory of Austria-Hungary, which triggered a series of war declarations in Europe with its declaration of war against Serbia on July 28, 1914. Croatian troops largely fought against the armies of Serbia, Russia, and Italy. Croatia seceded from Austria-Hungary in 1918 as a direct result of WWI.
Bosnia and Herzegovina	Central Powers	Secondary	1914	Europe	Bosnia and Herzegovina was a territory of Austria-Hungary at the start of WWI. The city of Sarajevo was the site of the June 28, 1914 assassination of Archduke Franz Ferdinand, which would trigger a series of war declarations in Europe.
Namibia	Central Powers	Minor	1914	Africa	At the start of WWI, Namibia was colony of Germany, which entered the war on Aug. 1, 1914. Namibia was invaded and taken over by troops from what is now South Africa, which was a British colony at the time.
Slovenia	Central Powers	Principal	1914	Europe	Slovenia at the time of WWI was a territory of Austria-Hungary, which triggered a series of war declarations in Europe with its declaration of war against Serbia on July 28, 1914. Slovenia's Isonzo Front was one of the bloodiest frontlines in WWI, with approximately 1.7 million people (mostly Italians and Slovenians) killed or maimed. After the war, Slovenia would join the newly formed Kingdom of Yugoslavia.
Samoa	Central Powers	Minor	1914	Oceania	Western Samoa was a German colony at the time of the war. It surrendered to New Zealand in August 1914 and was occupied by New Zealand through the end of the war.
Micronesia	Central Powers	Minor	1914	Oceania	A colony of Germany, which entered the war on August 1, 1914; the islands were captured and occupied by Japan in 1914.
Marshall Islands	Central Powers	Minor	1914	Oceania	A colony of Germany, which entered the war on August 1, 1914; the islands were captured by Japan in Oct. 1914 and occupied through the end of the war.
Nauru	Central Powers	Minor	1914	Oceania	Nauru was a German colony during WWI. It was captured by Australia in September 1914 and remained occupied through the end of the war.
India	Allies	Secondary	1914	Asia	Most of WWI-era India was part of the British Empire, and so entered the war in 1914 alongside Great Britain. More than a million troops from India served in the British military. Moreover, a small portion of modern India was part of the French Empire, and more than 700 soldiers from French India are known to have served in the French Colonial Army.
China	Allies	Minor	1917	Asia	China's involvement in World War I was minimal, as the country was consumed by internal political strife for much of the war's duration. However, it did dispatch laborers to France and deploy a small number of troops to Siberia.
Nigeria	Allies	Secondary	1914	Africa	Nigeria spent WWI as a freshly-minted colony of Great Britain, which declared war on Germany on August 4, 1914. A five-battalion Nigerian Regiment served in the Cameroons (1914-1916), and in the East African Campaign (1916-1918).
Russia	Allies	Principal	1914	Europe	Aligned with Serbia. Mobilized after Austria-Hungary's declaration of war in July 1914. Dissolved in 1917, amid the Russian Revolution.
Japan	Allies	Principal	1914	Asia	Japan played a significant role in World War I by capturing and occupying many German territories in the Pacific.
Egypt	Allies	Secondary	1914	Africa	Egypt during WWI was a protectorate of Great Britain, which declared war against Germany on Aug. 4, 1914, thereby drawing Egypt into the war by association. Some 55,000 Egyptians were conscripted to serve alongside British forces in both support and combat roles.
Vietnam	Allies	Secondary	1914	Asia	Often referred to as French Indochina (or just Indochina), Vietnam was administered by New Caledonia, a colony of France. Vietnamese islanders are known to have fought in the war, though the approximate number continues to be investigated. An estimated 40,000 Vietnamese men served in Allied combat battalions in Verdun.
United Kingdom	Allies	Principal	1914	Europe	The largest global empire at the time of the war, the United Kingdom declared war against Germany on Aug. 4, 1914. When the UK entered the war, its many colonies and dominions joined by default alongside it.
France	Allies	Principal	1914	Europe	When France, a principal ally, joined the war in 1914, its many colonial territories also joined by association. However, not all experienced the same level of conflict. France itself lost 1.3 million soldiers and 400,000 civilians over the course of World War I and arguably suffered more extensive physical damage than any other country.
South Africa	Allies	Secondary	1914	Africa	A self-governing dominion of the British Empire at the time of WWI, South Africa played a major role in the capture of German South West Africa (modern Namibia).
Kenya	Allies	Secondary	1914	Africa	Most of modern-day Kenya's territory was located in British East Africa (also known as the East African Protectorate), a protectorate of Great Britain which joined the war alongside Great Britain in 1914.
Myanmar	Allies	Secondary	1914		Then known as Burma, modern-day Myanmar spent WWI as a territory of the British Raj (a colony of Great Britain), which declared war against Germany on Aug. 4, 1914. Many captured Turkish (and some German) soldiers were held as prisoners of war in Burma, which also supplied troops, engineers, and laborers to the Allies.
Uganda	Allies	Minor	1914	Africa	A protectorate of Great Britain, which entered in the war in August 1914; Ugandan soldiers served in the East African Campaign.
Algeria	Allies	Secondary	1914	Africa	Part of French empire 1830-1951. Algerian soldiers fought in the French army. Nearly 60% of North African soldiers conscripted into the French military were from Algeria.
Canada	Allies	Secondary	1914	North America	Due to its ties to the British government, Canada joined the war automatically alongside Great Britain in August 1914. Canada deployed an "expeditionary force" of 620,000 soldiers, nurses, and chaplains, of whom 67,000 were killed and 173,000 wounded.
Angola	Allies	Secondary	1914	Africa	A colony of Portugal, Angola began fighting off a German invasion in December 1914, nearly two years before Portugal's declaration of war against Germany. Angola was the site of clashes between Portuguese troops and German forces stationed in German South West Africa (now Namibia)
Morocco	Allies	Minor	1914	Africa	At the time of WWI, Morocco was split between French (Allies) Morocco and Spanish (Neutral) Morocco. Most of the country was a protectorate of the French empire, which supported the Allies. However, Moroccans were actively rebelling at the time.
Malaysia	Allies	Secondary	1914	Asia	Malaysia was a British colony during WWI, and so joined the war by association alongside Great Britain on Aug. 4, 1914.
Mozambique	Allies	Secondary	1916	Africa	Mozambique spent WWI as a colony (Portuguese East Africa) of Portugal, which officially entered the war on March 9, 1916 after Germany’s declaration.
Saudi Arabia	Allies	Secondary	1915	Asia	Aided by France and Great Britain, the Saudis rebelled against the occupying Ottoman Empire, which was allied with the Central Powers. Contemporary Saudi Arabia includes territory that at the time was part of several now-dissolved countries, including Asir, The Emirate of Nejd and Hasa, and the Kingdom of Hejaz.
Madagascar	Allies	Secondary	1914	Africa	Madagascar spent WWI as a colony of France, which entered the war in 1914. At least 41,355 individuals from Madagascar served as part of French forces.
Ivory Coast	Allies	Secondary	1914	Africa	At the time of WWI, Ivory Coast was part of French West Africa, a colony of France, which entered the war in August 1914. More than 175,000 Ivorian men were conscripted in the French military. Approximately 135,000 served overseas, and more than 30,000 were killed in action.
Niger	Allies	Secondary	1914	Africa	A colony of France, which entered the war in August 1914
Australia	Allies	Secondary	1914	Oceania
Mali	Allies	Minor	1914	Africa	Modern-day Mali was a colony of France during WWI, so it joined the war by association. Recruits from the country served mainly in the Senegalese Tirailleurs, an infantry group made up of recruits from France's African colonies and protectorates. From 1915 to 1917, the people of French West Africa (esp. Burkina Faso and Mali) rebelled against forced conscription, forced labor, and French rule in general. The uprisings came to be known as the Volta-Bani War.
Burkina Faso	Allies	Minor	1914	Africa	Modern-day Burkina Faso was a colony of France during WWI, so it joined the war by association. Recruits from the country served mainly in the Senegalese Tirailleurs, an infantry group made up of recruits from France's African colonies and protectorates. From 1915 to 1917, the people of French West Africa (esp. Burkina Faso and Mali) rebelled against forced conscription, forced labor, and French rule in general. The uprisings came to be known as the Volta-Bani War.
Malawi	Allies	Secondary	1914	Africa	Malawi, then known alternately as Nyasaland, spent WWI as a colony of Great Britain, which declared war on Germany on Aug. 4, 1914.
Zambia	Allies	Secondary	1914	Africa	Then known as Northern Rhodesia, modern-day Zambia was a colony of Great Britain during WWI and a site of the East African campaign. Fighting in Africa didn't formally cease until Nov. 25, 1918, when German general Paul von Lettow-Vorbeck surrendered to the Allies in Abercorn, Northern Rhodesia.
Chad	Allies	Secondary	1914	Africa	Modern Chad was a French colony (part of French Equatorial Africa) during WWI, and so joined the war by association alongside France, which entered the war in August 1914.
Somalia	Allies	Minor	1914	Africa	Somalia was divided into British Somaliland (British colony), Italian Somaliland (Italian colony) and French Somaliland at the time of WWI (Ethiopia held territory as well). However, the colonial powers' hold was tenuous in many regions. In British Somaliland, for example, local freedom fighters forced British forces to evacuate for several months in 1916-1917. Despite such challenges, Somalia sent significant supplies to Italy and at least 2,434 Somalis (mostly from British Somaliland) are known to have served in the French Colonial Army.
Senegal	Allies	Secondary	1914	Africa	A colony of France, which entered the war in August 1914. At least 181,512 Senegalese are known to have served in the French Colonial Army.
Romania	Allies	Secondary	1916	Europe	Approximately three years after the end of the Second Balkan War, in which it fought against Bulgaria, Romania entered the war on behalf of the Allies and again engaged Bulgaria, which had aligned itself with the Central Powers.
Cambodia	Allies	Secondary	1914	Asia	Modern-day Cambodia (often referred to at the time as Indochina / French Indochina) was a French colony during WWI. It joined the war by association alongside France in August 1914.
Zimbabwe	Allies	Secondary	1914	Africa	A colony of Great Britain during WWI, modern Zimbabwe was then known as Southern Rhodesia. Nearly 40% of Zimbabwe's male population served in the war. The 1st Rhodesia Native Regiment was established in 1916 with 500 African troops and European officers, and fought in the East Africa campaign.
Guinea	Allies	Secondary	1914	Africa	Modern-day Guinea was a French colony during WWI. It joined the war by association alongside France in August 1914.
Benin	Allies	Secondary	1914	Africa	Benin was a colony of France during WWI (part of French Dahomey / French West Africa) and so joined the war by association. Over the course of the war, the Benini people rebelled against forced conscription by colonial authorities.
Tunisia	Allies	Minor	1914	Africa	Tunisia was a colony of France, which entered the war in August 1914.
Azerbaijan	Allies	Secondary	1914	Asia	Modern Azerbaijan began WWI as part of the Russian Empire, a Principal Allied participant. However, Azerbaijan declared its independence following the Russian Revolution of 1917 and the splintering of the short-lived Transcaucasian Democratic Federative Republic. It was annexed by the USSR in 1922 before regaining its independence in 1991.
Belarus	Allies	Principal	1914	Europe	Belarus began WWI as a territory of Russia, but spent large portions of the war occupied by Germany. Belarus was the site of significant clashes between German, Russian, and Polish forces, and thousands of Belarusians were displaced. Belarus declared its independence upon the signing of the Treaty of Brest-Litovsk in Brest in 1918, but instead hosted a war between Poland and Russia that ended with the two countries dividing Belarus among them in 1920. Belarus would eventually declare independence for good in 1990.
Sierra Leone	Allies	Minor	1914	Africa	A colony of Great Britain, which declared war on Germany on August 4, 1914
Laos	Allies	Secondary	1914	Asia	Part of Indochina/French Indochina, modern Laos was a colony of France during WWI, and entered the war by association alongside France in August 1914.
Serbia	Allies	Principal	1914	Europe	After diplomacy failed to resolve the conflict following the assassination of the Austro-Hungarian heir, Archduke Franz Ferdinand, Austria-Hungary declared war on Serbia on July 28, 1914. This event marked the official start of World War I
Republic of the Congo	Allies	Secondary	1914		A colony of France, which entered the war in August 1914.
Singapore	Allies	Minor	1914	Asia	Singapore was part of the British colony the Straits Settlements during World War I, and so joined the war alongside the UK in 1914. However, the country's involvement in the war was minimal
Liberia	Allies	Minor	1917	Africa	Neutral for the first few years, then declared war against Germany on Aug. 4, 1917. Liberian troops served in France, but did not see combat. However, the country did nationalize considerable German assets and withstood both shelling attacks and a German submarine blockade.
Finland	Allies	Secondary	1914	Europe	The Grand Duchy of Finland was a territory of the Russian Empire from the start of the war until the Finnish Civil War in 1918 between the Reds and Whites. Finland declared itself an independent republic in 1919.
Central African Republic	Allies	Secondary	1914	Africa	The modern Central African Republic was a French colony (part of French Equatorial Africa) during WWI, and so joined the war by association alongside France, which entered the war in August 1914.
Mauritania	Allies	Minor	1914	Africa	Part of French Empire, which entered the war in August 1914.
Ireland	Allies	Principal	1914		At the time of WWI, Ireland was a territory of mainland Great Britain, which declared war against Germany on Aug. 4, 1914. More than 200,000 Irish soldiers served in the British military.
New Zealand	Allies	Secondary	1914	Oceania	A colony of Great Britain, which declared war on Germany on August 4, 1914. New Zealand supplied 100,000 soldiers (10% of its population at the time) to the Allied cause, and also contributed financial and material support to both soldiers and military medical personnel.
Kuwait	Allies	Minor	1914	Asia	Kuwait was in the process of separating from the Ottoman Empire when WWI broke out. When British forces attacked Iraq in November 1914, Kuwait sent troops to attack Ottoman positions, which led Great Britain to recognize Kuwait as an "independent government under British protection."
Eritrea	Allies	Secondary	1915	Africa	A colony of Italy during WWI, Eritrea sent thousands of troops (called "askaris") to fight on the front lines in Africa, particularly on the Libyan front. Eritrea also produced and supplied the Italian military with approximately 12 million tins of canned meat over the course of the war.
Armenia	Allies	Secondary	1914	Asia	Modern Armenia was located largely within the Russian Empire at the time of WWI, and an estimated 150,000 Armenians joined the Russian army and fought for the allies. Armenia later became independent and again aligned itself with the Allies. It was annexed by the USSR in 1922 before regaining its independence in 1991.
Jamaica	Allies	Secondary	1914	North America	Jamaica was a British colony at the time of WWI, and so joined the war by association along with Great Britain in August 1914. More than 10,000 Jamaican troops served in the British West Indies Regiment,
Lithuania	Allies	Principal	1914	Europe	Lithuania spent WWI as a territory of Russia, which entered the war in July 1914. However, it was occupied by German forces from 1915 until the end of the war. Lithuanians actually fought on both sides of the war, some alongside Russian forces and some alongside the Germans. Due to the occupation, thousands of Lithuanians were displaced from their homes. It is estimated that as many Lithuanians died from diseases such as malaria, cholera, and dysentery as died in combat.
Gambia	Allies	Secondary	1914	Africa	Modern-day Gambia was a British West African colony during WWI. It joined the war by association alongside Great Britain in August 1914. Gambian soldiers served in the West African Regiment in Sierra Leone and the West African Frontier Force (WAFF) and their service included assisting in the Allied invasion of German Kamerun (now Cameroon).
Gabon	Allies	Secondary	1914	Africa	A colony of France, which entered the war in August 1914. Gabon was part of French Equatorial Africa, which also included Chad, French Congo, and Ubangi-Shari.
Botswana	Allies	Secondary	1914	Africa	Modern-day Botswana was a colony (Bechuanaland) of Great Britain during WWI, so it joined the war by association. Some Botswanans served in the unarmed South African Native Labour Contingent in France
Lesotho	Allies	Minor	1914	Africa	Then known as Basutoland, modern Laos was a British colony of France during WWI, and entered the war by association alongside Great Britain in August 1914. Basutoland's role in the war was minor.
Guinea Bissau	Allies	Minor	1916	Africa	Guinea-Bissau spent WWI as a colony of Portugal, which officially entered the war on March 9, 1916 in response to Germany’s declaration of war. Its involvement in the war was minimal.
Latvia	Allies	Principal	1914	Europe	Modern-day Latvia was part of the Russian Empire at the time of WWI, and so entered the war in July 1914 along with Russia. Latvia was the site of significant combat during WWI and was partly occupied by Germany 1915-1917 and fully occupied in 1918. More than 700,000 Latvians became refugees.
North Macedonia	Allies	Secondary	1914	Europe	North Macedonia during WWI was a territory of Serbia, which entered the war on July 28, 1914 after Austria-Hungary's declaration. North Macedonia was the site of considerable fighting during the war.
Trinidad and Tobago	Allies	Minor	1914	North America	Trinidad was a British colony at the time of WWI, and so joined the war by association along with Great Britain in August 1914. Trinidadian troops served in the British West Indies Regiment.
Timor Leste	Allies	Secondary	1916	Asia	A colony of Portugal, which officially entered the war on March 9, 1916 after Germany's declaration.
Cyprus	Allies	Secondary	1914	Europe	Modern-day Cyprus was a British colony (British Cyprus) during WWI. It joined the war by association alongside Great Britain on August 04,1914.
Estonia	Allies	Principal	1914	Europe	Estonia was a territory of Russia, which entered the war in July 1914. Approximately 100,000 Estonians were conscripted into the Russian military.
Mauritius	Allies	Minor	1914	Africa	A colony of Great Britain, which declared war on Germany on August 4, 1914
Eswatini	Allies	Secondary	1914	Africa	Known as Swaziland, Eswatini was a British colony during WWI. It joined the war by association alongside Great Britain, which entered the war in August 1914.
Djibouti	Allies	Minor	1914	Africa	Known as French Somaliland during WWI, Djibouti was part of the French Empire and so joined the war by association in 1914. Up to 2,000 soldiers from French Somaliland, known as “Tirailleurs Somalis” or “Bataillon Somali”, served as part of the French Army, including the battle of Verdun in 1916 and at the Chemin des Dames in 1917.
Comoros	Allies	Secondary	1914	Africa	Comoros was part of Madagascar, which in turn was a colony of France during WWI, and so entered the war by association in August 1914.
Reunion	Allies	Minor	1914		Reunion spent WWI as part of French Madagascar, a colony of France, which entered the war in August 1914. Some 6,936 Reunionese soldiers are known to have served in the French Colonial Army.
Guyana	Allies	Minor	1914	South America	Guyana was the colony British Guiana at the time of WWI, and so joined the war by association along with Great Britain in August 1914. Troops from Guyana served in the British West Indies Regiment.
Montenegro	Allies	Secondary	1914	Europe	Declared war against Germany on Aug. 11, 1914. Montenegro was occupied by Austria-Hungary throughout much of the war.
Malta	Allies	Secondary	1914	Europe	Malta spent WWI as a British colony, and so joined the war by default alongside Great Britain in 1914. Malta became a major hub for Allied medical services, treating more than 130,000 Allied soldiers over the course of the war.
Maldives	Allies	minor	1914	Asia	A protectorate of Great Britain, which declared war on Germany on August 4, 1914. The Maldives' role in the war was minimal, though it did contribute financially to the British war effort.
Cape Verde	Allies	Secondary	1916		Modern-day Cape Verde was a Portuguese colony during WWI, so it joined the war by association alongside Portugal in 1914. Cape Verde's ports were targeted by German U-Boats.
Belize	Allies	Secondary	1914	North America	Modern-day Belize was the colony British Honduras at the time of WWI, and so joined the war by association along with Great Britain in August 1914. Troops from British Honduras served in the British West Indies Regiment.
Bahamas	Allies	Minor	1914	North America	The Commonwealth of The Bahamas was a British colony during WWI and so became involved by association. An estimated 1,800 Bahamian troops served in militaries of UK, United States, and Canada.
Guadeloupe	Allies	Minor	1914		A colony of France, which entered the war in August 1914. Guadeloupe's participation in the war was minimal, though it did contribute funds to help support France's war effort. Also, 9,151 Guadeloupeans are known to have served in the French Colonial Army.
Martinique	Allies	Minor	1914		A colony of France, which entered the war in August 1914. Martinique's participation in the war was minimal, though it did contribute funds to help support France's war effort. 11,615 Martiniquan soldiers are known to have served in the French Colonial Army.
Mayotte	Allies	Minor	1914		Part of Madagascar, a colony of France, which entered the war in August 1914
Vanuatu	Allies	Minor	1914	Oceania	Known as the New Hebrides Condominium during WWI, the country now known as Vanuatu was administered dually by Great Britain and France. Vanuatu was home to 600 people of European heritage at the time of the war; of those, 18 British men served overseas.
French Guiana	Allies	Minor	1914		Although part of the French Empire during WWI, French Guiana was largely a penal colony at the time and had minimal participation in the war. However, some 1,929 French Guianese soldiers are known to have served in the French Colonial Army.
New Caledonia	Allies	Secondary	1914		A colony of France; men of fighting age from the island's indigenous population, the Kanaks, were conscripted into the French military during the war.
Barbados	Allies	Minor	1914	North America	Barbados was a British colony during WWI and so became involved by association. Barbadians served voluntarily in the British military, particularly in the British West Indies Regiment.
Sao Tome and Principe	Allies	Secondary	1916		São Tomé and Principe spent WWI as a colony of Portugal, which officially entered the war on March 9, 1916 after Germany’s declaration.
Saint Lucia	Allies	Minor	1914	North America	Saint Lucia was a British colony at the time of WWI, and so joined the war by association along with Great Britain in August 1914. Troops from Saint Lucia served in the British West Indies Regiment.
Kiribati	Allies	Minor	1914	Oceania	At the time of WWI, Kiribati was part of the Gilbert and Ellice Islands, a colony of Great Britain, which entered the war in August 1914. Eligible islanders served with New Zealand's forces.
Seychelles	Allies	Minor	1914	Africa	A colony of Great Britain, which declared war on Germany on August 4, 1914
Grenada	Allies	Minor	1914	North America	Grenada was a British colony during WWI, and so entered the war by association. It helped supply funding for the British war effort and contributed a small number of troops to the British West Indies Regiment.
Isle of Man	Allies	Secondary	1914		A British Crown dependency. During the war, over 82% of its men of fighting age enlisted in the British military.
Gibraltar	Allies	Minor	1914		Gibraltar was a colony of Great Britain, which declared war against Germany on August 4, 1914, during WWI. Residents of the colony established the Gibraltar Volunteer Corps for domestic defense, and its naval base served an important role for both the British and US naval forces.
Saint Martin	Allies	Minor	1914		A colony of France, which entered the war in August 1914
Cook Islands	Allies	Minor	1914		The Cook Islands were a colony of Great Britain, which declared war on Germany on Aug. 4, 1914, during World War 1. Soldiers from the Cook Islands served alongside regiments from New Zealand.
Saint Barthelemy	Allies	Minor	1914		A colony of France, which entered the war in August 1914
Wallis and Futuna	Allies	Minor	1914		A colony of France, which entered the war in August 1914
Tuvalu	Allies	Minor	1914	Oceania	At the time of WWI, Kiribati was part of the Gilbert and Ellice Islands, a colony of Great Britain, which entered the war in August 1914. Kaipati, the only known serviceman from Tuvalu, served alongside New Zealand forces.
Saint Pierre and Miquelon	Allies	Minor	1914		A colony of France, which entered the war in August 1914
Falkland Islands	Allies	Minor	1914		A colony of Great Britain, which declared war on Germany on August 4, 1914; site of the Battle of the Falkland Islands on December 8. 1914.
Tokelau	Allies	Minor	1914		A colony of Great Britain, which entered the war in August 1914; awarded to New Zealand in the Treaty of Versailles.
Pakistan				Asia
Bangladesh				Asia
DR Congo				Africa
Iran				Asia
South Korea				Asia
Afghanistan				Asia
Uzbekistan				Asia
Nepal				Asia
North Korea				Asia
Sri Lanka				Asia
Taiwan				Asia
Kazakhstan				Asia
United Arab Emirates				Asia
Tajikistan				Asia
Turkmenistan				Asia
Hong Kong				Asia
Kyrgyzstan				Asia
Denmark				Europe
Oman				Asia
Mongolia				Asia
Qatar				Asia
Fiji				Oceania
Solomon Islands				Oceania
Bhutan				Asia
Macau				Asia
Suriname				South America
Brunei				Asia
Saint Vincent and the Grenadines				North America
Antigua and Barbuda				North America
Dominica				North America
Saint Kitts and Nevis				North America
Liechtenstein				Europe
Monaco				Europe
Palau				Oceania
Vatican City				Europe

Data are based upon each country’s government and borders at the time of WWI, which may differ from their modern incarnations.
Participants that have dissolved since WWI, such as the Ottoman Empire, are typically listed under the names of the countries that currently exist in their place.
Participants that are not classified as sovereign states by the United Nations, such as the Andaman Islands, may not be listed.
Countries are placed into one of three categories based upon their level of involvement in WWI:
“Principal” countries were major participants in WWI
“Secondary” countries were slightly less impactful than principal combatants but still played important roles in WWI, such as providing supplies, sending large number of troops, or enduring military attack or occupation.
“Minor” countries played comparatively small roles in the war, but were still involved in some way, such as providing aid or sending small numbers of troops to serve in a primary participants army.
Many countries’ alignments shifted over the course of the war. For example, a country that was initially neutral may have been drawn into the fray by invasion from another country, and a country whose government allied with one side could switch allegiances after an internal coup replaced that government with new leadership.
Occupied countries present a unique case, as it could be argued they aided their occupiers’ efforts, although they did so grudgingly and without choice in the matter.
Perhaps surprisingly, sources disagree as to the date upon which WWI ended. Most commemorations mark the ending as 11 November, 1918, the date upon which the Armistice of Compiègne was signed, ending hostilities. However, some memorials maintain that WWI did not truly end until the signing of the Versaille Treaty on 28 June 1919.

World War I (abbreviated WWI or WW1) was a global war that was started in Europe on July 28, 1914. This war lasted for over four years, finally coming to an end on November 11, 1918. This war was not only long, but it was also one of the largest wars in history. Over 70 million military personnel were mobilized, including 60 million Europeans. This war was also very deadly, resulting in the death of approximately 9 million servicemen and 7 million civilians.

The first event that led to the war was the assassination of Archduke Franz Ferdinand by Gavrilo Princip. Following the assassination, Serbia and Austria-Hungary went to war. The war grew as a result of interlocking alliances. Europe was divided into two coalitions: the Triple Alliance and the Triple Entente. Then, a domino effect began. Russia was ready to defend Serbia, its ally. Then, Germany declared war on Russia in order to protect Austria. France in turn declared war on Germany to protect Russia. Then, Britain declared war on Germany after the Germans invaded Belgium. On one side, the countries that were involved in this war included Austria-Hungary, Bulgaria, Germany, and the Ottoman Empire. Fighting against them was France, Great Britain, italy, Japan, Romania, Russia, and the United States. The war finally came to an end in 1917 with the signing of the Treaty of Versailles.

Countries Involved in World War 1 (WWI)

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