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Allies of World War II

Grouping of the victorious countries of World War II

Top 10 Allies of World War II related articles

Allies of World War II

StatusMilitary alliance
Historical eraWorld War II
Feb 1921
Aug 1939
Sep 1939–Jun 1940
Jun 1941
Jul 1941
Aug 1941
Jan 1942
Nov–Dec 1943
1–15 Jul 1944
4–11 Feb 1945
Apr–Jun 1945
Jul–Aug 1945
    1. ^ 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.
    2. ^ France declared war on Germany on 3 September 1939, two days after the German invasion of Poland. It was a member of the Allies until its defeat in the German invasion of France in June 1940. Unlike the other governments-in-exile in London, which were legitimate governments that had escaped their respective countries and continued the fight, France had surrendered to the Axis. The "Free French Forces" was a section of the French army who 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. After the gradual liberation of Vichy colonial territory by Free France, a National Liberation Committee was formed. The loss of colonies eventually led to the full German occupation of Vichy France in 1942, which started a shift in allied policy from trying to improve relations with the Vichy Regime into full support of the now Provisional Government of the French Republic.
    3. ^ The Ethiopian Empire was invaded by Italy on 3 October 1935. On 2 May 1936, Emperor 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.
    4. ^ 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.
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
The Allied leaders of the Asian and Pacific Theater: Generalissimo Chiang Kai-shek, Franklin D. Roosevelt, and Winston Churchill meeting at the Cairo Conference in 1943

The Allies of World War II were the countries that together opposed the Axis powers during the Second World War (1939–1945). The Allies promoted the alliance as a means to defeat German, Japanese and Italian aggression.

At the start of the war on 1 September 1939, the Allies consisted of Poland, the United Kingdom, and France as well as their dependent states, such as British India. They were joined by the independent Dominions of the British Commonwealth: Canada, Australia, New Zealand and South Africa.[1] After the start of the German invasion of North Europe until the Balkan Campaign, the Netherlands, Belgium, Greece, and Yugoslavia joined the Allies. After first having cooperated with Germany in invading Poland whilst remaining neutral in the Allied-Axis conflict, the Soviet Union perforce joined the Allies in June 1941 after being invaded by Germany. The United States provided war materiel and money to the Allies all along, and officially joined in December 1941 after the Japanese attack on Pearl Harbor. China had already been in a prolonged war with Japan since the Marco Polo Bridge Incident of 1937 and officially joined the Allies in December 1941.

The alliance was formalized by the Declaration by United Nations, from 1 January 1942. However, the name "United Nations" was rarely used to describe the Allies during the war. The leaders of the "Big Three"—the Soviet Union, the United Kingdom, and the United States—controlled Allied strategy; relations between the United Kingdom and the United States were especially close. The Big Three together with China were referred as a "trusteeship of the powerful",[2] then were recognized as the Allied "Big Four" in the Declaration by United Nations[3] and later as the "Four Policemen" of the United Nations. After the war ended, the Allied states became the basis of the modern United Nations.[4]

Allies of World War II Intro articles: 30

Origins and creation

The origins of the Allied powers stem from the Allies of World War I and cooperation of the victorious powers at the Paris Peace Conference, 1919. Germany resented signing the Treaty of Versailles. The new Weimar Republic's legitimacy became shaken. However, the 1920s were peaceful.

With the Wall Street Crash of 1929 and the ensuing Great Depression, political unrest in Europe soared including the rise in support of revanchist nationalists in Germany who blamed the severity of the economic crisis on the Treaty of Versailles. By the early 1930s, the Nazi Party led by Adolf Hitler became the dominant revanchist movement in Germany and Hitler and the Nazis gained power in 1933. The Nazi regime demanded the immediate cancellation of the Treaty of Versailles and made claims to German-populated Austria, and German-populated territories of Czechoslovakia. The likelihood of war was high, and the question was whether it could be avoided through strategies such as appeasement.

In Asia, when Japan seized Manchuria in 1931, the League of Nations condemned it for aggression against China. Japan responded by leaving the League of Nations in March 1933. After four quiet years, the Sino-Japanese War erupted in 1937 with Japanese forces invading China. The League of Nations condemned Japan's actions and initiated sanctions on Japan. The United States, in particular, was angered at Japan 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, Germany took over Czechoslovakia, violating the Munich Agreement signed six months before, and demonstrating that the appeasement policy was a failure. Britain and France decided that Hitler had no intention to uphold diplomatic agreements and responded by preparing for war. On 31 March 1939, Britain formed the Anglo-Polish military alliance in an effort to avert a German attack on the country. Also, the French had a long-standing alliance with Poland since 1921. The Soviet Union sought an alliance with the western powers, but Hitler ended the risk of a war with Stalin by signing the Nazi–Soviet non-aggression pact in August 1939. 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. Then, on 17 September 1939, 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 and it continued to be one of the Allies. After a quiet winter, Germany in April 1940 invaded and quickly defeated Denmark, Norway, Belgium, the Netherlands and France. Britain and its Empire stood alone against Hitler and Mussolini.

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.

In June 1941, Hitler broke the non-aggression agreement with Stalin and Germany invaded the Soviet Union, and the Soviet Union declared war on Germany. Britain agreed an alliance with the Soviet Union in July. The Atlantic Conference followed in August 1941 between American President Franklin Roosevelt and British Prime Minister Winston Churchill. 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 by Britain and United States. In December, Japan attacked the US and Britain resulting in a state of war between the US and the Axis powers, with whom China also declared war. The main lines of World War II had formed. The alliance was formalised in the Declaration by United Nations signed in January 1942.

Allies of World War II Origins and creation articles: 37

Major affiliated state combatants

During December 1941, U.S. President Franklin D. Roosevelt devised the name "United Nations" for the Allies and proposed it to British Prime Minister Winston Churchill.[5][6] He referred to the Big Three and China as a "trusteeship of the powerful", and then later the "Four Policemen".[2] The Declaration by United Nations on 1 January 1942 was the basis of the modern United Nations (UN).[7] At the Potsdam Conference of July–August 1945, Roosevelt's successor, Harry S. Truman, proposed that the foreign ministers of China, France, the Soviet Union, the United Kingdom, and the United States "should draft the peace treaties and boundary settlements of Europe", which led to the creation of the Council of Foreign Ministers of the "Big Five", and soon thereafter the establishment of those states as the permanent members of the UNSC.[8]

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
British aircraft carrier HMS Ark Royal under attack from Italian aircraft during the Battle of Cape Spartivento (27 Nov. 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; these countries were Canada, India and South Africa as well as Nepal.

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".[9]

Africa colonies and dependencies

British West Africa and the British colonies in East and Southern Africa participated, mainly in the North African, East African and Middle-Eastern theatres. Two West African and one East African division served in the 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.[10]

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 1933–49, 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.

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 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.

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

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

In Europe

The Cyprus Regiment was formed by the British Government during the Second World War and made part of the British Army structure. It was mostly Greek Cypriot volunteers and Turkish-speaking Cypriot inhabitants of Cyprus but also included other Commonwealth nationalities. On a brief visit to Cyprus in 1943, Winston Churchill praised the "soldiers of the Cyprus Regiment who have served honourably on many fields from Libya to Dunkirk". About 30,000 Cypriots served in the Cyprus Regiment. The regiment was involved in action from the very start and served at Dunkirk, in the 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

FAFL Free French GC II/5 "LaFayette" receiving ex-USAAF Curtiss P-40 fighters at Casablanca, 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.[11] 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.[11]

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

Colonies and dependencies

In Africa

In Africa these included: French West Africa, French Equatorial Africa, the League of Nations mandates of French Cameroun and French Togoland, French Madagascar, French Somaliland, and the protectorates of French Tunisia and French Morocco.

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

In 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 these included: French Polynesia, Wallis and Futuna, New Caledonia, the New Hebrides, French Indochina, French India, the mandates of Greater Lebanon and French Syria. The French government in 1936 attempted to grant independence to its mandate of Syria in the Franco-Syrian Treaty of Independence of 1936 signed by France and Syria. However, opposition to the treaty grew in France and the treaty was not ratified. Syria had become an official republic in 1930 and was largely self-governing. In 1941, a British-led invasion supported by Free French forces expelled Vichy French forces in operation Exporter.

In the Americas

In the Americas these included: 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
Soviet 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.[13] 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".[13]

Stalin had studied Hitler, including reading Mein Kampf and from it knew of Hitler's motives for destroying the Soviet Union.[14] 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.[15] However, Poland withdrew from the negotiations following German and Finnish objections.[15] The Soviet Union and Germany at this time competed with each other for influence in Poland.[16] The Soviet government also was concerned with the anti-Soviet sentiment in Poland and particularly Józef Piłsudski's proposed Polish federation that would include the territories of Poland, Lithuania, Belarus, and Ukraine within it that threatened the territorial integrity of the Soviet Union.[17]

On 20 August 1939, forces of the Union of Soviet Socialist Republics under General Georgy Zhukov, together with the People's Republic of Mongolia eliminated the threat of conflict in the east with a victory over Imperial Japan at 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.)[18]

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".[19]

On 15 September 1939, Stalin concluded a durable ceasefire with Japan, to take effect the following day (it would be upgraded to a non-aggression pact in April 1941).[20] The day after that, 17 September, Soviet forces invaded Poland from the east. Although some fighting continued until 5 October, the two invading armies held at least one joint military parade on 25 September, and reinforced their non-military partnership with the 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.[21][22]

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,[23] the USSR militarily[24] occupied and annexed Estonia, Latvia, and Lithuania[25] as well as parts of Romania.

German-Soviet treaties were brought to an end by the German surprise attack on the USSR on 22 June 1941. After the invasion of the Soviet Union in 1941, Stalin endorsed the Western Allies as part of a renewed popular front strategy against Germany and called for the international communist movement to make a coalition with all those who opposed the Nazis.[13] The Soviet Union soon entered in alliance with the United Kingdom. Following the USSR, a number of other communist, pro-Soviet or Soviet-controlled forces fought against the Axis powers during the Second World War. They were as follows: the Albanian National Liberation Front, the Chinese Red Army, the Greek National Liberation Front, the Hukbalahap, the Malayan Communist Party, the People's Republic of Mongolia, the Polish People's Army, the Tuvan People's Republic (annexed by the Soviet Union in 1944),[26] the Viet Minh and the Yugoslav Partisans.

The Soviet Union intervened against Japan and its client state in Manchuria in 1945, cooperating with the Nationalist Government of China and the Nationalist Party led by Chiang Kai-shek; though also cooperating, preferring, and encouraging the Communist Party led by Mao Zedong to take effective control of Manchuria after expelling Japanese forces.[27]

United States

American Douglas SBD Dauntless dive-bomber aircraft attacking the Japanese cruiser Mikuma during the Battle of Midway in June 1942
U.S. Marines during the 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
U.S. soldiers departing landing craft during the Normandy landings on 6 June 1944 known as D-Day

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".[28] 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.[29] 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.[30] 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 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.[31] A major turning point in the Pacific War was the Battle of Midway where American naval forces were outnumbered by Japanese forces that had been sent to Midway to draw out and destroy American aircraft carriers in the Pacific and seize control of Midway that would place Japanese forces in proximity to Hawaii.[32] However American forces managed to sink four of Japan's six large aircraft carriers that had initiated the attack on Pearl Harbor along with other attacks on Allied forces. Afterwards the US began an offensive against Japanese-captured positions. 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 Alaska, the Panama Canal Zone, Puerto Rico, and the U.S. Virgin Islands.

In the Pacific it held multiple island dependencies such as American Samoa, Guam, Hawaii, Midway Islands, Wake Island and others. These dependencies were directly involved in the Pacific campaign of the war.

In Asia
Philippine Scouts at 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 Kuomintang, or the Nationalists and helped reorganize their party along 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 total war. Following the 1931 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 anti-communist military campaigns after his kidnap and release by Zhang Xueliang, and reluctantly formed a nominal alliance with the Communists, while the Communists agreed to fight under the nominal command of the Nationalists against the Japanese. Following the Marco Polo Bridge Incident of 7 July 1937, China and Japan became embroiled in a full-scale war. The Soviet Union, wishing to keep China in the fight against Japan, supplied China with military assistance until 1941, when it signed a non-aggression pact with Japan. China formally declared war on Japan, as well as Germany and Italy, in December 1941, after the attack on Pearl Harbor.

Continuous clashes between the Communists and Nationalists behind enemy lines cumulated in a major military conflict between these two former allies that effectively ended their cooperation against the Japanese, and China had been divided between the internationally recognized Nationalist China under the leadership of Generalissimo Chiang Kai-shek and 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.[33] 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.[33] Italy also held strong commercial interests and a strong commercial position in China supported by the Italian concession in Tianjin.[33] 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.[34]

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 percent 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.[35] 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.[36] US President Franklin D. Roosevelt accepted dispatching them to China in early 1941.[36] 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 Communist Party of China and inclusion of Communists in the government.[37] The Soviet Union also urged military and cooperation between Nationalist China and Communist China during the war.[37]

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.[37] 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.[37] The Soviet Union urged military and cooperation between Soviet China and Nationalist China during China's war against Japan.[37] 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".[38] 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.[38]

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.[39]

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.[40]

Allies of World War II Major affiliated state combatants articles: 239