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Countries Involved in World War Two (WWII) 2024

While a surprising number of countries are currently at war, all of today's conflicts combined would still be far smaller than World War II. Involving more than 100 million people from dozens of nations (many more than in World War I) spread all across the globe, WWII was the biggest war in human history. It was also the deadliest war in history, resulting in an estimated 21-25 million military casualties and 50-55 civilian deaths—including the more than 6 million Jews who were killed in Nazi concentration camps. Leading up to the war, many countries attempted to remain neutral. However, as the conflict raged on, more and more countries were forced to join one of two sides: the Allies and the Axis Powers.

Both of these alliances changed and morphed over the course of the war, with countries coming and going as battles were won and lost, territories were taken and liberated, and political agreements were forged and dissolved. Several countries started out as neutral but were eventually drawn into the conflict, or initially fought for one side, but switched to the other (often after a forceful change in government). As a result, several countries were both Allies and Axis, or both neutral and either Allies/Axis.

Which countries joined the Allies in World War II?

When World War II began in 1939, the Allies were France, Poland, and the United Kingdom. Days later, the independent British dominions of Australia, Canada, New Zealand, and South Africa joined. As the war continued, more and more countries joined the Allies—including two major powers which had intended to remain neutral.

The first of these powers was Russia, which had signed a non-aggression pact with Germany and had even participated in Germany's initial invasion of Poland. However, when Germany broke that pact and invaded Russia in Operation Barbarossa in June 1941, Russia quickly joined the Allies.

The second formerly neutral power was the United States, whose entry into the war was prompted by Axis power Japan's attack on Pearl Harbor in December 1941. China also joined the Allies in December 1941—though the country had already been at war with Japan since 1937.

The Allied countries were led by the "Four Powers," which consisted of the "Big Three"—the United Kingdom, United States, and Russia—as well as China. More than twenty additional countries also contributed to the cause. The Allies would formalize their union with the Declaration of United Nations, which was signed by the Four Powers on January 01, 1942, and 22 more countries on January 02. The declaration would become the United Nations Charter with the formal launch of the United Nations in 1945.

Countries on the Allies side in WWII:

CountryDate JoinedCountryDate JoinedCountryDate Joined
Argentina27 March 1945Finland*15 Sept. 1944Oman10 Sept. 1939
Australia3 Sept. 1939France3 Sept. 1939Panama7 Dec. 1941
Belgium10 May 1940Greece28 Oct 1940Paraguay7 Feb. 1945
Bolivia7 Apr. 1943Guatemala9 Dec. 1941Peru12 Feb. 1945
Brazil22 Aug. 1942Haiti8 Dec 1941Philippines8 Dec 1941
British India3 Sept. 1939Honduras8 Dec. 1941Poland1 Sept. 1939
Bulgaria*8 Sept. 1944Iran9 Sept. 1943Romania*25 Aug. 1944
Canada10 Sept. 1939Iraq16 Jan. 1943Saudi Arabia1 Mar. 1945
Chile11 April 1945Lebanon27 Feb. 1945South Africa6 Sept. 1939
China9 Dec 1941Italy*10 Oct. 1943South Korea*10 Dec. 1941
Colombia26 July 1943Liberia27 Jan. 1944Soviet Union22 June 1941
Costa Rica8 Dec. 1941Luxembourg10 May 1940Syria26 Feb. 1945
Cuba9 Dec. 1941Mexico22 May 1942Turkey23 Feb. 1945
Czechoslovakia*16 Dec. 1941Mongolia1 Aug 1945United Kingdom3 Sept. 1939
Denmark8 Apr. 1940Nepal4 Sept. 1939United States8 Dec. 1941
Dominican Rep.8 Dec. 1941Netherlands10 May 1940Uruguay15 Feb. 1945
Ecuador2 Feb. 1945New Zealand3 Sept. 1939Venezuela15 Feb. 1945
Egypt24 Feb. 1945Nicaragua8 Dec. 1941Vietnam (Viet Minh)7 Dec. 1941
El Salvador8 Dec. 1941Norway8 Apr. 1940Yugoslavia6 Apr. 1941
Ethiopia14 Dec. 1942

* Notes:

  • Bulgaria was a former Axis nation.
  • Czechoslovakia's government was in exile at the time of declaration.
  • Finland fought alongside Germany and against Russia in the Continuation War from 1941-1944, declared war on Germany on 3 March 1945, but made the declaration retroactive to 15 September 1944.
  • Italy and Romania were former Axis nations.
  • South Korea's government was provisional.
  • Vietnam's allegiance came courtesy of the Viet Minh.

Which countries joined the Axis powers in World War II?

The three major Axis powers were Germany, Italy, and Japan, which banded together under a series of agreements, culminating in the Tripartite Pact of 1940. Six additional nations then joined the Tripartite Pact. The first four were fairly straightforward: Hungary on November 20, 1940, Romania on November 23, Slovakia on November 24, Bulgaria on March 1, 1941.

The final two signatories on the Tripartite Pact come with caveats. First is Yugoslavia, whose government feared a German invasion if they chose to resist, and so signed the pact on March 25, 1941—however, the government was promptly overthrown by a coup and the new government rejected the agreement a mere two days later. (This act prompted Germany to add Yugoslavia to the list of countries it had invaded.) Lastly, the German-Italian puppet state of Croatia signed on April 10, 1941, despite the fact that it was an illegitimate nation with no actual authority to do so.

In addition to the Tripartite Pact, certain other countries signed what was known as the Anti-Comintern Pact, which was much less demanding. Many Anti-Comintern countries were allowed to remain neutral or required to send only volunteer troops to join the Nazi army. Even less binding were the Bilateral Pacts that other countries (as well as a few illegitimate governments and Nazi-installed puppet states) agreed to follow. Additionally, the Axis powers, particularly Japan, also made extensive use of "puppet states," in which a newly overtaken country's existing government would be replaced by a new (typically illegitimate) government that operated on its own but took its orders from the "puppetmaster" country.

Countries on the Axis side in WWII:

BulgariaAxisLaos*puppet state
Burma (Ba Maw govt)*bilateral pactManchuko*puppet state
Cambodia (Kampuchea)*puppet stateMongolia (Mengjiang)*puppet state
CroatiaAxisPhilippines (Second Republic)*puppet state
GermanyAxisSoviet Union*bilateral pact
Greece (Hellenic States)puppet stateSpainAnti-Comintern
HungaryAxisThailandbilateral pact
India (Azad Hind)*puppet stateVichy France*puppet state
Iraqbilateral pactVietnam (Empire of Vietnam)*puppet state

* Notes:

  • Denmark's contributions were minimal and it would likely have remained neutral if it had not been occupied by Germany during much of the war.
  • Finland never actually joined the Axis, but fought alongside Germany against Russia in the Continuation War from 1941-1944.
  • The Soviet Union helped Germany invade Poland before switching to the Allies.
  • Yugoslavia agreed to join the Axis, but the agreement was rejected two days later after a government coup.
  • All other Axis countries marked with * were puppet states, illegitimate governments, or both.

Which countries remained neutral in World War II?

As difficult a task as it was, several countries did manage to remain neutral during World War II. Many officially neutral countries nonetheless offered limited support to one side or the other, such as sending volunteer troops or allowing passage through their territory.

Neutral Countries in WWII:

IranSan MarinoVatican City
IrelandSaudi ArabiaYemen

When did WWII start and end?

It is generally accepted that World War II began on September 1, 1939, when German troops invaded Poland, prompting the leaders of France and Britain to declare war two days later. However, as this conflict expanded, it merged with existing hostilities between Japan and several other countries in Asia. Because of this, some historians suggest that WWII actually began as early as July 7, 1937, the start of the Second Sino-Japanese War, or when Japan invaded Manchuria on September 19, 1931. The war's end date is also debatable. Most historians agree that the end date was August 14, 1945, also known as V-J (Victory over Japan) day. Technically, however, the war didn't end until September 2, 1945, the day Japan formally surrendered.

  • Many countries have complex WWII histories. See Additional Details column for clarification.
  • List includes notable occupied territories and puppet insurgencies that were not officially recognized countries and were dissolved at the war's conclusion.

Download Table Data

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Axis or Allies
WWII Time Line
Additional Details
TurkeyNeutralTurkey was neutral until several months before the end of the war. Turkey was an important producer of chromite, a strategic material for metallurgy to which Germany had limited access. The Germans wanted it, and the Allies wanted to prevent them from getting it. So, chromite was the key issue in Turkey's negotiations with both sides. Turkey halted its sales to Germany in April 1944 and broke off relations in August. In February 1945 and then declared war on the Axis powers, but no Turkish troops ever saw combat.
SpainNeutralSpain, whose civil war had just ended at the beginning of World War II, sent troops to the Russian front to help German armed forces
ArgentinaNeutralBecause of strong divisions and internal disputes between members of the Argentine military, the country would continue to remain neutral, even after American sanctions. However, Argentina eventually gave in to the Allies' pressure, broke relations with the Axis powers on January 26, 1944, and declared war on March 27, 1945. More than 4,000 Argentine volunteers fought on the Allied side.
Saudi ArabiaNeutralAlthough officially neutral, the Saudis provided the Allies with large supplies of oil. Diplomatic relations with the United States were established in 1943. King Abdul Aziz Al-Saud was a personal friend of Franklin D. Roosevelt. Saudi Arabia declared war on Germany on 28 February 1945 and Japan on 1 April 1945, but no military actions resulted from the declaration.
SwedenNeutralThe transit of German troops through Finland and Sweden and Swedish iron-ore mining during World War II helped the German war effort. | Danish resistance worked with Sweden to carry out the 1943 rescue of the Danish Jews by shipping them to Sweden. During the Liberation of Finnmark, Sweden sent Norwegian "police" troops over the border to link up with Allied forces. At the end of the war, Sweden was preparing to join the Allied invasion of Norway and Denmark if the occupying Wehrmacht forces rejected a general armistice.
PortugalNeutralPortugal granted access to the British to its bases in the Azores
SwitzerlandNeutralNazis purchased critical war material from neutral countries using Swiss francs gained in exchange for gold looted by the Nazis from occupied countries and from individual victims of concentration camps. Switzerland continued to trade until the end of the war in 1945.
IrelandNeutralÉamon de Valera the Taoiseach (head of government), refrained from joining either side, although he generally favored and aided the Allied powers by allowing access to their naval repair yards.
LithuaniaNeutralThe Baltic states of Estonia, Latvia, and Lithuania, jointly declared their neutrality on 18 November 1938, in Riga, at the Conference of Baltic Foreign Ministers with their respective parliaments passing neutrality laws later that year. Despite that, all of them were occupied twice by the Soviet Union and once by Nazi Germany.
LatviaNeutralThe Baltic states of Estonia, Latvia, and Lithuania, jointly declared their neutrality on 18 November 1938, in Riga, at the Conference of Baltic Foreign Ministers with their respective parliaments passing neutrality laws later that year. Despite that, all of them were occupied twice by the Soviet Union and once by Nazi Germany.
EstoniaNeutralThe Baltic states of Estonia, Latvia, and Lithuania, jointly declared their neutrality on 18 November 1938, in Riga, at the Conference of Baltic Foreign Ministers with their respective parliaments passing neutrality laws later that year. Despite that, all of them were occupied twice by the Soviet Union and once by Nazi Germany.
IcelandNeutralOccupied by Allied forces from May 1940>
MonacoNeutralMonaco was occupied by Italy and later by Germany.
San MarinoNeutralSan Marino was briefly occupied by Germany on 17–20 September 1944. The occupation led the microstate to declare war on Germany on 21 September 1944.
Vatican CityNeutral
JapanAxisSeptember 22, 1940 - September 2, 1945
GermanyAxisSeptember 1, 1939 - May 8–9, 1945
ItalyAxisJune 1940 - September 8, 1943.Originally one of the major Axis powers, Italy left the Axis once its dictatorial ruler, Benito Mussolini, was removed. Although Italy did not join the Allies, it did declare war on Germany, making it a co-belligerent which fought alongside the Allies.
RomaniaAxisNovember 23, 1940 - August 23, 1944Originally an Axis power, Romania surrendered to Russia in 1944 and subsequently became an Allied participant.
HungaryAxisNovember 20, 1940 - March 1944In March 1944, Germany forced Hungary to accept occupation by German forces. Hungary never surrendered. The war ended for Hungary in early April 1945.
LaosAxisLaos at the time of WWII was a puppet state ruled by Japan.
BulgariaAxisMarch 1, 1941 - September 8, 1944Bulgaria was part of the Axis powers from 1941-1944. It was invaded by Allied Russia and its government forced into exile in 1944. The new government joined the Allies for the final year of the war.
SlovakiaAxisNovember 24, 1940 - early April 1945Part of Czechoslovakia at the time of the war, much of what is now Slovakia was split off as a German satellite state (the Slovak Republic) upon Germany's annexation of the rest of Czechoslovakia. The Slovak Republic rejoined Czechoslovakia in 1945. Czechoslovakia split into two countries again, amicably this time, on December 31, 1992. Most citizens of modern-day Slovakia consider their country a successor to Czechoslovakia, but not to the Slovak Republic.
CroatiaAxisJune 15, 1941
ChinaAlliesDecember, 1941China had been at war with Japan since July 1937. It declared war on Japan, Germany and Italy and joined the Allies in December 1941 after the attacks on Pearl Harbor.
United StatesAlliesDecember 11. 1941
BrazilAlliesAugust 22, 1942
RussiaAlliesJune 22, 1941Russia's predecessor country, the U.S.S.R (commonly referred to as Russia, or the Soviet Union) joined WW2 on behalf of the Axis powers on September 17, 1939, when it invaded eastern Poland in coordination with Nazi Germany. USSR changed sides to the Allies after Operation Barbarossa on June 22, 1941, when it was invaded by Germany.
EthiopiaAlliesJuly, 1940The Ethiopian Empire was invaded by Italy on 3 October 1935. On 2 May 1936, Emperor Haile Selassie I fled into exile. After the outbreak of World War II, the United Kingdom recognized Haile Selassie as the Emperor of Ethiopia in July 1940 and his Ethiopian exile government cooperated with the British during their invasion of Italian East Africa in 1941. Through the invasion Haile Selassie returned to Ethiopia on 18 January, with the liberation of the country being completed by November the same year.
MexicoAlliesMay 22, 1942
PhilippinesAlliesDecember 8, 1941
IranAlliesIran was initially neutral but was occupied by the Allies. It later declared war on Germany in 1943.
United KingdomAlliesSeptember 3, 1939
FranceAlliesSeptember 3, 1939
South AfricaAlliesSeptember 1939
PolandAlliesSeptember 1, 1939
CanadaAlliesSeptember 1939
AustraliaAlliesSeptember 1939
GuatemalaAlliesDecember, 1941
NetherlandsAlliesMay, 1940
BoliviaAlliesApril 7, 1943
HaitiAlliesDecember, 1941
BelgiumAlliesMay, 1940
Dominican RepublicAlliesDecember, 1941
CubaAlliesDecember, 1941
HondurasAlliesDecember, 1941
Czech RepublicAlliesMarch 15, 1939Part of Czechoslovakia at the time. Czechoslovakia's democratic government spent much of the war in exile due to Germany's occupation of Czechoslovakia, so the government's joining of the Allies was more ceremonial than functional.
GreeceAlliesOctober 28, 1940
El SalvadorAlliesDecember, 1941
DenmarkAlliesApril 9, 1940Did not join Axis and supplied only volunteer troops, but was occupied by Germany through much of the war.
FinlandAlliesJune 26, 1941 - September 19, 1944Finland entered the war against the USSR as a “co-belligerent.” The Finns sought to regain territory lost during the 1939–1940 Winter War with the Soviet Union. Finland never signed the Tripartite Pact or entered into a formal alliance with Nazi Germany. On September 19, 1944 Finland signed an armistice with the Soviet Union. Finland did not officially declare war on Germany until 3 March 1945, but made the declaration retroactive.
NorwayAlliesApril 9, 1940
New ZealandAlliesSeptember 1939
Costa RicaAlliesDecember, 1941
PanamaAlliesDecember, 1941
MongoliaAllies10 August 1945
LuxembourgAlliesMay, 1940
showing: 63 rows

Which countries were involved in World War II?

Most countries joined the Allied or Axis powers. The Allies included the United States, the United Kingdom, Russia, and China. The Axis powers included Germany, Italy, and Japan.

How many countries were involved in World War II?

Only 21 countries remained neutral during World War II. The others choose to side with the Allied powers or the Axis side.

Frequently Asked Questions