Allies of World War II

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Allies of World War II
同盟國/同盟国 (Chinese)
Alliés (French)
Антигитлеровская коалиция (Russian)
  •   Allies and their colonies
  •   Allies entering after the attack on Pearl Harbor
  •   Axis powers, co-belligerents, and their colonies
  •   Neutral powers and their colonies

Other Allied combatant states:

Co-belligerents (former Axis powers):
Anglo-Polish alliance
August 1939
September 1939 – June 1940
June 1941
July 1941
August 1941
January 1942
May 1942
November–December 1943
1–15 July 1944
4–11 February 1945
April–June 1945
July–August 1945
Succeeded by
United Nations
    1. Free French Forces" were a section of the French army which refused to recognize the armistice and continued to fight with the Allies. They worked towards France being seen and treated as a major allied power, as opposed to a defeated and then liberated nation. They struggled with legitimacy vis-a-vis the German client state "Vichy France", which was the internationally recognized government of France even among the Allies. A National Liberation Committee was formed by the Free French after the gradual liberation of Vichy colonial territory, which led to the full German occupation of Vichy France in 1942. This started a shift in Allied policy from trying to improve relations with the Vichy regime into full support to what was now the Provisional Government of the French Republic
    2. ^ The Polish Underground State was allied with United Kingdom and United States. It fought against Axis Powers (mostly Germany), Soviet Union and the Polish Committee of National Liberation (PKWN). However the PKWN was allied with the Soviet Union and fought against Germany and the Polish Underground State.
    3. ^ Edvard Beneš, president of the First Czechoslovak Republic, fled the country after the 1938 Munich Agreement saw the Sudetenland region annexed by Germany. In 1939 a German sponsored Slovak Republic seceded from the post-Munich Second Czechoslovak Republic, providing justification for the establishment of a German protectorate over the remaining Czech lands (the rump Carpathian Ruthenia region being annexed by Hungary). Following the outbreak of war later the same year, Beneš, in his exile, formed a Czechoslovak National Liberation Committee which after some months of negotiations regarding its legitimacy became regarded as the Czechoslovak government-in-exile by the Allies.
    4. Haile Selassie I fled into exile, just before the Italian occupation on 7 May. 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.
    5. ^ China 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.
Three men, Stalin, Roosevelt and Churchill, sitting together elbow to elbow
The Allied leaders of the European theatre (left to right): Joseph Stalin, Franklin D. Roosevelt and Winston Churchill meeting at the Tehran Conference in 1943
Cairo Conference
in 1943
French postcard illustrating the alliance between Poland, France and the United Kingdom (1939)
"Long live the victory of the Anglo-Soviet-American military alliance!" – USSR stamp of 1943, quoting Stalin

The Allies, formally referred to as the United Nations from 1942, were an international military coalition formed during World War II (1939–1945) to oppose the Axis powers. Its principal members by the end of 1941 were the "Big Four" – the United Kingdom, United States, Soviet Union, and China.

Membership in the Allies varied during the course of the war. When the conflict broke out on 1 September 1939, the Allied coalition consisted of the United Kingdom,

since 1937
, and formally joined the Allies in December 1941.

The Allies were led by the so-called "Big Three"—the United Kingdom, the Soviet Union, and the United States—which were the principal contributors of manpower, resources, and strategy, each playing a key role in achieving victory.[2][3][4] A series of conferences between Allied leaders, diplomats, and military officials gradually shaped the makeup of the alliance, the direction of the war, and ultimately the postwar international order. Relations between the United Kingdom and the United States were especially close, with their bilateral Atlantic Charter forming the groundwork of their alliance.

The Allies became a formalized group upon the Declaration by United Nations on 1 January 1942, which was signed by 26 nations around the world; these ranged from governments in exile from the Axis occupation to small nations far removed from the war. The Declaration officially recognized the Big Three and China as the "Four Powers",[5] acknowledging their central role in prosecuting the war; they were also referred to as the "trusteeship of the powerful", and later as the "Four Policemen" of the United Nations.[6] Many more countries joined through to the final days of the war, including colonies and former Axis nations. After the war ended, the Allies, and the Declaration that bound them, would become the basis of the modern United Nations;[7] one enduring legacy of the alliance is the permanent membership of the U.N. Security Council, which is made up exclusively of the principal Allied powers that won the war.


The victorious Allies of World War I—which included what would become the Allied powers of the Second World War—had imposed harsh terms on the opposing Central Powers in the Paris Peace Conference of 1919–1920. Germany resented signing the Treaty of Versailles, which required that it take full responsibility for the war, lose a significant portion of territory, and pay costly reparations, among other penalties. The Weimar Republic, which formed at the end of the war and subsequently negotiated the treaty, saw its legitimacy shaken, particularly as it struggled to govern a greatly weakened economy and humiliated populace.

The Wall Street Crash of 1929, and the ensuing Great Depression, led to political unrest across Europe, especially in Germany, where revanchist nationalists blamed the severity of the economic crisis on the Treaty of Versailles. The far-right Nazi Party led by Adolf Hitler, which had formed shortly after the peace treaty, exploited growing popular resentment and desperation to become the dominant political movement in Germany. By 1933, they gained power and rapidly established a totalitarian regime known as Nazi Germany. The Nazi regime demanded the immediate cancellation of the Treaty of Versailles and made claims over German-populated Austria and the German-populated territories of Czechoslovakia. The likelihood of war was high, but none of the major powers had the appetite for another conflict; many governments sought to ease tensions through nonmilitary strategies such as appeasement.

Japan, which was a principal allied power in the First World War, had since become increasingly militaristic and imperialistic; parallel to Germany, nationalist sentiment increased throughout the 1920s, culminating in the invasion of Manchuria in 1931. The League of Nations strongly condemned the attack as an act of aggression against China; Japan responded by leaving the League in 1933. The second Sino-Japanese War erupted in 1937 with Japan's full-scale invasion of China. The League of Nations condemned Japan's actions and initiated sanctions; the United States, which had attempted to peacefully negotiate for peace in Asia, was especially angered by the invasion and sought to support China.

British wartime poster supporting Poland after the German invasion of the country (European theater)
American wartime poster promoting aid to China during the Second Sino-Japanese War (Pacific theater)

In March 1939,

alliance with Poland since 1921

The Soviet Union, which had been diplomatically and economically isolated by much of the world, had sought an alliance with the western powers, but Hitler preempted a potential war with Stalin by signing the Nazi–Soviet non-aggression pact in August 1939. In addition to preventing a two-front war that had battered its forces in the last world war, the agreement secretly divided the independent states of Central and Eastern Europe between the two powers and assured adequate oil supplies for the German war machine.

On 1 September 1939, Germany invaded Poland; two days later Britain and France declared war on Germany. Roughly two weeks after Germany's attack, the Soviet Union invaded Poland from the east. Britain and France established the Anglo-French Supreme War Council to coordinate military decisions. A Polish government-in-exile was set up in London, joined by hundreds of thousands of Polish soldiers, which would remain an Allied nation until the end. After a quiet winter, Germany began its invasion of Western Europe in April 1940, quickly defeating Denmark, Norway, Belgium, the Netherlands, and France. All the occupied nations subsequently established a government-in-exile in London, with each contributing a contingent of escaped troops. Nevertheless, by roughly one year since Germany's violation of the Munich Agreement, Britain and its Empire stood alone against Hitler and Mussolini.

Formation of the "Grand Alliance"

Before they were formally allied, the United Kingdom and the United States had cooperated in a number of ways,

British Commonwealth and, to a lesser extent, the Soviet Union reciprocated with a smaller Reverse Lend-Lease program.[10][11]

The First Inter-Allied Meeting took place in London in early June 1941 between the United Kingdom, the four co-belligerent British Dominions (Canada, Australia, New Zealand and South Africa), the eight governments in exile (Belgium, Czechoslovakia, Greece, Luxembourg, the Netherlands, Norway, Poland, Yugoslavia) and Free France. The meeting culminated with the Declaration of St James's Palace, which set out a first vision for the postwar world.

In June 1941, Hitler broke the non-aggression agreement with Stalin and Axis forces

Atlantic Conference between American President Franklin Roosevelt and British Prime Minister Winston Churchill, which defined a common Anglo-American vision of the postwar world, as formalized by the Atlantic Charter.[13]

At the Second Inter-Allied Meeting in London in September 1941, the eight European governments in exile, together with the Soviet Union and representatives of the Free French Forces, unanimously adopted adherence to the common principles of policy set forth in the Atlantic Charter. In December, Japan attacked American and British territories in Asia and the Pacific, resulting in the U.S. formally entering the war as an Allied power. Still reeling from Japanese aggression, China declared war on all the Axis powers shortly thereafter.

By the end of 1941, the main lines of World War II had formed. Churchill referred to the "Grand Alliance" of the United Kingdom, the United States, and the Soviet Union,[14][15] which together played the largest role in prosecuting the war. The alliance was largely one of convenience for each member: the U.K. realized that the Axis powers threatened not only its colonies in North Africa and Asia but also the homeland. The United States felt that the Japanese and German expansion should be contained, but ruled out force until Japan's attack. The Soviet Union, having been betrayed by the Axis attack in 1941, greatly despised German belligerence and the unchallenged Japanese expansion in the East, particularly considering their defeat in previous wars with Japan; the Soviets also recognized, as the U.S. and Britain had suggested, the advantages of a two-front war.

The Big Three

Queen Elizabeth and Princess Elizabeth talking to paratroopers in preparation of D-Day, 19 May 1944
World War II military deaths in Europe and military situation in autumn 1944

Franklin D. Roosevelt, Winston Churchill, and Joseph Stalin were The Big Three leaders. They were in frequent contact through ambassadors, top generals, foreign ministers and special emissaries such as the American Harry Hopkins. It is also often called the "Strange Alliance", because it united the leaders of the world's greatest capitalist state (the United States), the greatest socialist state (the Soviet Union) and the greatest colonial power (the United Kingdom).[16]

Relations between them resulted in the major decisions that shaped the war effort and planned for the postwar world.[4][17] Cooperation between the United Kingdom and the United States was especially close and included forming a Combined Chiefs of Staff.[18]

There were numerous high-level conferences; in total Churchill attended 14 meetings, Roosevelt 12, and Stalin 5. Most visible were the three summit conferences that brought together the three top leaders.[19][20] The Allied policy toward Germany and Japan evolved and developed at these three conferences.[21]

  • Tehran Conference (codename "Eureka") – first meeting of The Big Three (28 November 1943 1 December 1943)
  • Yalta Conference (codename "Argonaut") – second meeting of The Big Three (4–11 February 1945)
  • Potsdam Conference (codename "Terminal") – third and final meeting of The Big Three (Truman having taken over for Roosevelt, 17 July – 2 August 1945)


There were many tensions among the Big Three leaders, although they were not enough to break the alliance during wartime.[3][22]

In 1942 Roosevelt proposed becoming, with China, the Four Policemen of world peace. Although the 'Four Powers' were reflected in the wording of the Declaration by United Nations, Roosevelt's proposal was not initially supported by Churchill or Stalin.

Division emerged over the length of time taken by the Western Allies to establish a second front in Europe.[23] Stalin and the Soviets used the potential employment of the second front as an 'acid test' for their relations with the Anglo-American powers.[24] The Soviets were forced to use as much manpower as possible in the fight against the Germans, whereas the United States had the luxury of flexing industrial power, but with the "minimum possible expenditure of American lives".[24] Roosevelt and Churchill opened ground fronts in North Africa in 1942 and in Italy in 1943, and launched a massive air attack on Germany, but Stalin kept wanting more.

Although the U.S. had a strained relationship with the USSR in the 1920s, relations were normalized in 1933. The original terms of the Lend-Lease loan were amended towards the Soviets, to be put in line with British terms. The United States would now expect interest with the repayment from the Soviets, following the initiation of the Operation Barbarossa, at the end of the war—the United States were not looking to support any "postwar Soviet reconstruction efforts",[25] which eventually manifested into the Molotov Plan. At the Tehran conference, Stalin judged Roosevelt to be a "lightweight compared to the more formidable Churchill".[26][27] During the meetings from 1943 to 1945, there were disputes over the growing list of demands from the USSR.

Tensions increased further when Roosevelt died and his successor

Harry Truman rejected demands put forth by Stalin.[23] Roosevelt wanted to play down these ideological tensions.[28] Roosevelt felt he "understood Stalin's psychology", stating "Stalin was too anxious to prove a point ... he suffered from an inferiority complex."[29]

United Nations

Wartime poster for the United Nations, created in 1941 by the U.S. Office of War Information

Four Policemen

During December 1941, Roosevelt devised the name "United Nations" for the Allies and Churchill agreed.[30][31] He referred to the Big Three and China as the "Four Policemen" repeatedly from 1942.[32]

Declaration by United Nations

Wartime poster for the United Nations, created in 1943 by the U.S. Office of War Information

The alliance was formalised in the Declaration by United Nations signed on 1 January 1942. There were the 26 original signatories of the declaration; the Big Four were listed first:

Alliance growing

The United Nations began growing immediately after its formation. In 1942, Mexico, the Philippines and Ethiopia adhered to the declaration. Ethiopia had been restored to independence by British forces after the Italian defeat in 1941. The Philippines, still owned by Washington but granted international diplomatic recognition, was allowed to join on 10 June despite its occupation by Japan.

In 1943, the Declaration was signed by Iraq, Iran, Brazil, Bolivia and Colombia. A Tripartite Treaty of Alliance with Britain and the USSR formalised Iran's assistance to the Allies.[33] In Rio de Janeiro, Brazilian dictator Getúlio Vargas was considered near to fascist ideas, but realistically joined the United Nations after their evident successes.[citation needed]

In 1944, Liberia and France signed. The French situation was very confused. Free French forces were recognized only by Britain, while the United States considered Vichy France to be the legal government of the country until Operation Overlord, while also preparing U.S. occupation francs. Winston Churchill urged Roosevelt to restore France to its status of a major power after the liberation of Paris in August 1944; the Prime Minister feared that after the war, Britain could remain the sole great power in Europe facing the Communist threat, as it was in 1940 and 1941 against Nazism.

During the early part of 1945, Peru, Chile, Paraguay, Venezuela, Uruguay, Turkey, Egypt, Saudi Arabia, Lebanon, Syria (these latter two French colonies had been declared independent states by British occupation troops, despite protests by Pétain and later De Gaulle) and Ecuador became signatories. Ukraine and Belarus, which were not independent states but parts of the Soviet Union, were accepted as members of the United Nations as a way to provide greater influence to Stalin, who had only Yugoslavia as a communist partner in the alliance.

Major affiliated state combatants

Franklin Roosevelt, Winston Churchill, Joseph Stalin, Chiang Kai-shek and Charles de Gaulle were leaders of the Big Five

United Kingdom

British Supermarine Spitfire fighter aircraft (bottom) flying past a German Heinkel He 111 bomber aircraft (top) during the Battle of Britain in 1940
North African Campaign
British aircraft carrier HMS Ark Royal under attack from Italian aircraft during the Battle of Cape Spartivento (27 November 1940)
British soldiers of the King's Own Yorkshire Light Infantry in Elst, Netherlands on 2 March 1945

British Prime Minister, Neville Chamberlain delivered his Ultimatum Speech on 3 September 1939 which declared war on Germany, a few hours before France. As the Statute of Westminster 1931 was not yet ratified by the parliaments of Australia and New Zealand, the British declaration of war on Germany also applied to those dominions. The other dominions and members of the British Commonwealth declared war from 3 September 1939, all within one week of each other; they were Canada, British India and South Africa.[34]

During the war, Churchill attended seventeen Allied conferences at which key decisions and agreements were made. He was "the most important of the Allied leaders during the first half of World War II".[35]

African colonies and dependencies

Burma Campaign

Southern Rhodesia was a self-governing colony, having received responsible government in 1923. It was not a sovereign dominion. It governed itself internally and controlled its own armed forces, but had no diplomatic autonomy, and, therefore, was officially at war as soon as Britain was at war. The Southern Rhodesian colonial government issued a symbolic declaration of war nevertheless on 3 September 1939, which made no difference diplomatically but preceded the declarations of war made by all other British dominions and colonies.[36]

American colonies and dependencies

These included: the British West Indies, British Honduras, British Guiana and the Falkland Islands. The Dominion of Newfoundland was directly ruled as a royal colony from 1933 to 1949, run by a governor appointed by London who made the decisions regarding Newfoundland.


British India included the areas and peoples covered by later India, Bangladesh, Pakistan and (until 1937) Burma/Myanmar, which later became a separate colony.

British Malaya covers the areas of Peninsular Malaysia and Singapore, while British Borneo covers the area of Brunei, including Sabah and Sarawak of Malaysia.

British Hong Kong consisted of Hong Kong Island, the Kowloon Peninsula, and the New Territories.

Territories controlled by the Colonial Office, namely the Crown Colonies, were controlled politically by the UK and therefore also entered hostilities with Britain's declaration of war. At the outbreak of World War II, the British Indian Army numbered 205,000 men. Later during World War II, the British Indian Army became the largest all-volunteer force in history, rising to over 2.5 million men in size.

Indian soldiers earned 30 Victoria Crosses during the Second World War. It suffered 87,000 military casualties (more than any Crown colony but fewer than the United Kingdom). The UK suffered 382,000 military casualties.

Kuwait was a protectorate of the United Kingdom formally established in 1899. The Trucial States were British protectorates in the Persian Gulf.

Palestine was a mandate dependency created in the peace agreements after World War I from the former territory of the Ottoman Empire, Iraq.



Greek Campaign (about 600 soldiers were captured in Kalamata in 1941), North Africa (Operation Compass), France, the Middle East and Italy. Many soldiers were taken prisoner especially at the beginning of the war and were interned in various PoW camps (Stalag) including Lamsdorf (Stalag VIII-B
), Stalag IVC at Wistritz bei Teplitz and Stalag 4b near Most in the Czech Republic. The soldiers captured in Kalamata were transported by train to prisoner of war camps.


Free French forces at the Battle of Bir Hakeim
, 1942

War declared

, French Morocco
The French fleet scuttled itself
rather than fall into the hands of the Axis after their invasion of Vichy France on 11 November 1942.

After Germany invaded Poland, France declared war on Germany on 3 September 1939.[37] In January 1940, French Prime Minister Édouard Daladier made a major speech denouncing the actions of Germany:

At the end of five months of war, one thing has become more and more clear. It is that Germany seeks to establish a domination of the world completely different from any known in world history.

The domination at which the Nazis aim is not limited to the displacement of the balance of power and the imposition of the supremacy of one nation. It seeks the systematic and total destruction of those conquered by Hitler and it does not treaty with the nations which it has subdued. He destroys them. He takes from them their whole political and economic existence and seeks even to deprive them of their history and culture. He wishes only to consider them as vital space and a vacant territory over which he has every right.

The human beings who constitute these nations are for him only cattle. He orders their massacre or migration. He compels them to make room for their conquerors. He does not even take the trouble to impose any war tribute on them. He just takes all their wealth and, to prevent any revolt, he scientifically seeks the physical and moral degradation of those whose independence he has taken away.[37]

France experienced several major phases of action during World War II:

Colonies and dependencies


In Africa these included:

French Morocco

French Algeria was then not a colony or dependency but a fully-fledged part of metropolitan France.

Asia and Oceania
The fall of Damascus to the Allies, late June 1941. A car carrying Free French commanders General Georges Catroux and General Paul Louis Le Gentilhomme enters the city, escorted by French Circassian cavalry (Gardes Tcherkess).

In Asia and Oceania France has several territories:

Operation Exporter


France had several colonies in America, namely Martinique, Guadeloupe, French Guiana and Saint Pierre and Miquelon.

Soviet Union

Soviet soldiers and T-34 tanks advancing near Bryansk in 1942
Soviet soldiers fighting in the ruins of Stalingrad during the Battle of Stalingrad
Il-2 ground attack aircraft attacking German ground forces during the Battle of Kursk
, 1943


In the lead-up to the war between the Soviet Union and Nazi Germany, relations between the two states underwent several stages.

General Secretary Joseph Stalin and the government of the Soviet Union had supported so-called popular front movements of anti-fascists including communists and non-communists from 1935 to 1939.[39] The popular front strategy was terminated from 1939 to 1941, when the Soviet Union cooperated with Germany in 1939 in the occupation and partitioning of Poland. The Soviet leadership refused to endorse either the Allies or the Axis from 1939 to 1941, as it called the Allied-Axis conflict an "imperialist war".[39]

Stalin had studied Hitler, including reading Mein Kampf, and from it knew of Hitler's motives for destroying the Soviet Union.[40] As early as in 1933, the Soviet leadership voiced its concerns with the alleged threat of a potential German invasion of the country should Germany attempt a conquest of Lithuania, Latvia, or Estonia, and in December 1933 negotiations began for the issuing of a joint Polish-Soviet declaration guaranteeing the sovereignty of the three Baltic countries.[41] However, Poland withdrew from the negotiations following German and Finnish objections.[41] The Soviet Union and Germany at this time competed with each other for influence in Poland.[42]

On 20 August 1939, forces of the

Battle of Khalkhin Gol
in eastern Mongolia.

On the same day, Soviet party leader Joseph Stalin received a telegram from German Chancellor Adolf Hitler, suggesting that German Foreign Minister Joachim von Ribbentrop fly to Moscow for diplomatic talks. (After receiving a lukewarm response throughout the spring and summer, Stalin abandoned attempts for a better diplomatic relationship with France and the United Kingdom.)[43]

On 23 August, Ribbentrop and Soviet Foreign Minister Vyacheslav Molotov signed the non-aggression pact including secret protocols dividing Eastern Europe into defined "spheres of influence" for the two regimes, and specifically concerning the partition of the Polish state in the event of its "territorial and political rearrangement".[44]

On 15 September 1939, Stalin concluded a durable ceasefire with Japan, to take effect the following day (it would be upgraded to

German–Soviet Treaty of Friendship, Cooperation and Demarcation on 28 September. German and Soviet cooperation against Poland in 1939 has been described as co-belligerence.[46][47]

On 30 November, the Soviet Union attacked Finland, for which it was expelled from the League of Nations. In the following year of 1940, while the world's attention was focused upon the German invasion of France and Norway,[48] the USSR militarily[49] occupied and annexed Estonia, Latvia, and Lithuania[50] as well as parts of Romania.

German-Soviet treaties were brought to an end by the

Polish People's Army, the Tuvan People's Republic (annexed by the Soviet Union in 1944),[51] the Viet Minh and the Yugoslav Partisans

The Soviet Union intervened against Japan and its

Nationalist Government of China and the Nationalist Party led by Chiang Kai-shek; though also cooperating, preferring, and encouraging the Chinese Communist Party led by Mao Zedong to take effective control of Manchuria after expelling Japanese forces.[52]

United States

American Douglas SBD Dauntless dive-bomber aircraft attacking the Japanese cruiser Mikuma during the Battle of Midway in June 1942
Guadalcanal Campaign
in November 1942
American Consolidated B-24 Liberator bomber aircraft during the bombing of oil refineries in Ploiești, Romania on 1 August 1943 during Operation Tidal Wave

War justifications

The United States had indirectly supported Britain's war effort against Germany up to 1941 and declared its opposition to territorial aggrandizement. Materiel support to Britain was provided while the U.S. was officially neutral via the Lend-Lease Act starting in 1941.

President Franklin D. Roosevelt and Prime Minister Winston Churchill in August 1941 promulgated the Atlantic Charter that pledged commitment to achieving "the final destruction of Nazi tyranny".[53] Signing the Atlantic Charter, and thereby joining the "United Nations" was the way a state joined the Allies, and also became eligible for membership in the United Nations world body that formed in 1945.

The US strongly supported the Nationalist Government in China in its war with Japan, and provided military equipment, supplies, and volunteers to the Nationalist Government of China to assist in its war effort.[54] In December 1941 Japan opened the war with its attack on Pearl Harbor, the US declared war on Japan, and Japan's allies Germany and Italy declared war on the US, bringing the US into World War II.

The US played a central role in liaising among the Allies and especially among the Big Four.[55] At the Arcadia Conference in December 1941, shortly after the US entered the war, the US and Britain established a Combined Chiefs of Staff, based in Washington, which deliberated the military decisions of both the US and Britain.


On 8 December 1941, following the attack on Pearl Harbor, the United States Congress declared war on Japan at the request of President Franklin D. Roosevelt. This was followed by Germany and Italy declaring war on the United States on 11 December, bringing the country into the European theatre.

The US led Allied forces in the Pacific theatre against Japanese forces from 1941 to 1945. From 1943 to 1945, the US also led and coordinated the Western Allies' war effort in Europe under the leadership of General Dwight D. Eisenhower.

The surprise attack on Pearl Harbor followed by Japan's swift attacks on Allied locations throughout the Pacific, resulted in major US losses in the first several months in the war, including losing control of the Philippines, Guam, Wake Island and several Aleutian islands including Attu and Kiska to Japanese forces. American naval forces attained some early successes against Japan. One was the bombing of Japanese industrial centres in the Doolittle Raid. Another was repelling a Japanese invasion of Port Moresby in New Guinea during the Battle of the Coral Sea.[56]

A major turning point in the Pacific War was the

Guadalcanal Campaign from 1942 to 1943 was a major contention point where Allied and Japanese forces struggled to gain control of Guadalcanal

Colonies and dependencies

In the Americas and the Pacific

The United States held multiple dependencies in the Americas, such as

U.S. Virgin Islands

In the Pacific it held multiple island dependencies such as

and others. These dependencies were directly involved in the Pacific campaign of the war.

In Asia
Fort William McKinley
firing a 37 mm anti-tank gun in training

The Commonwealth of the Philippines was a sovereign protectorate referred to as an "associated state" of the United States. From late 1941 to 1944, the Philippines was occupied by Japanese forces, who established the Second Philippine Republic as a client state that had nominal control over the country.


In the 1920s the Soviet Union provided military assistance to the

Leninist lines: a unification of party, state, and army. In exchange the Nationalists agreed to let members of the Chinese Communist Party join the Nationalists on an individual basis. However, following the nominal unification of China at the end of the Northern Expedition in 1928, Generalissimo Chiang Kai-shek purged leftists from his party and fought against the revolting Chinese Communist Party, former warlords
, and other militarist factions.

A fragmented China provided easy opportunities for Japan to gain territories piece by piece without engaging in

Mukden Incident, the puppet state of Manchukuo
was established. Throughout the early to mid-1930s, Chiang's anti-communist and anti-militarist campaigns continued while he fought small, incessant conflicts against Japan, usually followed by unfavorable settlements and concessions after military defeats.

In 1936 Chiang was forced to cease his

signed a non-aggression pact with Japan

In December 1941 after the attack on Pearl Harbor, China formally declared war on Japan, as well as Germany and Italy. As part of the war's Pacific theater, China became the only member of the Allies to commit more troops than one of the Big Three,[58] exceeding even the number of Soviet troops on the Eastern Front.[59]

Continuous clashes between the Communists and Nationalists behind enemy lines cumulated in

Communist China under the leadership of Mao Zedong
until the Japanese surrendered in 1945.


Soldiers of the National Revolutionary Army associated with Nationalist China, during the Second Sino-Japanese War

Prior to the alliance of Germany and Italy to Japan, the Nationalist Government held close relations with both Germany and Italy. In the early 1930s,

Sino-German cooperation existed between the Nationalist Government and Germany in military and industrial matters. Nazi Germany provided the largest proportion of Chinese arms imports and technical expertise. Relations between the Nationalist Government and Italy during the 1930s varied, however even after the Nationalist Government followed League of Nations sanctions against Italy for its invasion of Ethiopia, the international sanctions proved unsuccessful, and relations between the Fascist government in Italy and the Nationalist Government in China returned to normal shortly afterwards.[60]

Up until 1936, Mussolini had provided the Nationalists with Italian military air and naval missions to help the Nationalists fight against Japanese incursions and communist insurgents.

Italian concession in Tianjin.[60] However, after 1936 the relationship between the Nationalist Government and Italy changed due to a Japanese diplomatic proposal to recognize the Italian Empire that included occupied Ethiopia within it in exchange for Italian recognition of Manchukuo, Italian Foreign Minister Galeazzo Ciano accepted this offer by Japan, and on 23 October 1936 Japan recognized the Italian Empire and Italy recognized Manchukuo, as well as discussing increasing commercial links between Italy and Japan.[61]

The Nationalist Government held close relations with the United States. The United States opposed Japan's invasion of China in 1937 that it considered an illegal violation of China's sovereignty, and offered the Nationalist Government diplomatic, economic, and military assistance during its war against Japan. In particular, the United States sought to bring the Japanese war effort to a complete halt by imposing a full embargo on all trade between the United States to Japan, Japan was dependent on the United States for 80 per cent of its petroleum, resulting in an economic and military crisis for Japan that could not continue its war effort with China without access to petroleum.[62] In November 1940, American military aviator Claire Lee Chennault upon observing the dire situation in the air war between China and Japan, set out to organize a volunteer squadron of American fighter pilots to fight alongside the Chinese against Japan, known as the Flying Tigers.[63] US President Franklin D. Roosevelt accepted dispatching them to China in early 1941.[63] However, they only became operational shortly after the attack on Pearl Harbor.

The Soviet Union recognised the Republic of China but urged reconciliation with the Chinese Communist Party and inclusion of Communists in the government.[64] The Soviet Union also urged military and cooperation between Nationalist China and Communist China during the war.[64]

Even though China had been fighting the longest among all the Allied powers, it only officially joined the Allies after the attack on Pearl Harbor, on 7 December 1941. China fought the Japanese Empire before joining the Allies in the Pacific War. Generalissimo Chiang Kai-shek thought Allied victory was assured with the entrance of the United States into the war, and he declared war on Germany and the other Axis states. However, Allied aid remained low because the Burma Road was closed and the Allies suffered a series of military defeats against Japan early on in the campaign. General Sun Li-jen led the R.O.C. forces to the relief of 7,000 British forces trapped by the Japanese in the Battle of Yenangyaung. He then reconquered North Burma and re-established the land route to China by the Ledo Road. But the bulk of military aid did not arrive until the spring of 1945. More than 1.5 million Japanese troops were trapped in the China Theatre, troops that otherwise could have been deployed elsewhere if China had collapsed and made a separate peace.

Soldiers of the First Workers' and Peasants' Army associated with Communist China, during the Sino-Japanese War
Victorious Chinese Communist soldiers holding the flag of the Republic of China during the Hundred Regiments Offensive

Communist China had been tacitly supported by the Soviet Union since the 1920s: though the Soviet Union diplomatically recognised the Republic of China, Joseph Stalin supported cooperation between the Nationalists and the Communists—including pressuring the Nationalist Government to grant the Communists state and military positions in the government.[64] This was continued into the 1930s that fell in line with the Soviet Union's subversion policy of popular fronts to increase communists' influence in governments.[64]

The Soviet Union urged military and cooperation between Communist China and Nationalist China during China's war against Japan.[64] Initially Mao Zedong accepted the demands of the Soviet Union and in 1938 had recognized Chiang Kai-shek as the "leader" of the "Chinese people".[65] In turn, the Soviet Union accepted Mao's tactic of "continuous guerilla warfare" in the countryside that involved a goal of extending the Communist bases, even if it would result in increased tensions with the Nationalists.[65]

After the breakdown of their cooperation with the Nationalists in 1941, the Communists prospered and grew as the war against Japan dragged on, building up their sphere of influence wherever opportunities were presented, mainly through rural mass organizations, administrative, land and tax reform measures favoring poor peasants; while the Nationalists attempted to neutralize the spread of Communist influence by military blockade and fighting the Japanese at the same time.[66]

The Communist Party's position in China was boosted further upon the Soviet invasion of Manchuria in August 1945 against the Japanese puppet state of Manchukuo and the Japanese Kwantung Army in China and Manchuria. Upon the intervention of the Soviet Union against Japan in World War II in 1945, Mao Zedong in April and May 1945 had planned to mobilize 150,000 to 250,000 soldiers from across China to work with forces of the Soviet Union in capturing Manchuria.[67]

Other affiliated state combatants


Albania was retroactively recognized as an "Associated Power" at the 1946 Paris conference[68] and officially signed the treaty ending WWII between the "Allied and Associated Powers" and Italy in Paris, on 10 February 1947.[69][70]


Australia was a sovereign Dominion under the Australian monarchy, as per the Statute of Westminster 1931. At the start of the war Australia followed Britain's foreign policies and accordingly declared war against Germany on 3 September 1939. Australian foreign policy became more independent after the Australian Labor Party formed government in October 1941, and Australia separately declared war against Finland, Hungary and Romania on 8 December 1941 and against Japan the next day.[71]


Members of the Belgian Resistance with a Canadian soldier in Bruges, September 1944 during the Battle of the Scheldt

Before the war, Belgium had pursued a policy of

being invaded by Germany on 10 May 1940. During the ensuing fighting, Belgian forces fought alongside French and British forces against the invaders. While the British and French were struggling against the fast German advance elsewhere on the front, the Belgian forces were pushed into a pocket to the north. On 28 May, the King Leopold III
surrendered himself and his military to the Germans, having decided the Allied cause was lost.

The legal Belgian government was reformed as

Free Belgian Forces. Belgium itself was occupied, but a sizeable Resistance
was formed and was loosely coordinated by the government in exile and other Allied powers.

British and Canadian troops arrived in Belgium in September 1944 and the capital,

Ardennes Offensive
, the country was only fully liberated in early 1945.

Colonies and dependencies

Belgium held the colony of the

East African Campaign against the Italians. The colonial Force Publique
also served in other theatres including Madagascar, the Middle-East, India and Burma within British units.