Allies of World War II
The Allies of World War II were an international military coalition that formed in opposition to the Axis powers during the war that ran from 1939 to 1945. On the 1st of January 1942, representatives of 26 countries gathered their signatures on a single document called the Declaration by United Nations. That moment formalized what had until then been a shifting, sometimes reluctant partnership into something with a name, a structure, and a shared pledge. The questions worth asking are not simply who fought on which side. They are how this coalition was assembled, what held it together despite deep ideological rifts, and how the decisions made around conference tables shaped not just the war but the entire postwar world.
The Treaty of Versailles in 1919 created the League of Nations as a mechanism for collective security, but the system carried a structural flaw from the start: the United States never joined. Japan's withdrawal from the League in February 1933, following criticism of its invasion of Manchuria, exposed that weakness further. Nazi Germany followed suit in October 1933. Italy invaded Abyssinia in October 1935, and the League responded with sanctions that proved weak and short-lived. Germany remilitarised the Rhineland in March 1936 in direct contravention of the Versailles and Locarno treaties, and Britain, France, and the League imposed no consequences. The Munich Agreement of the 30th of September 1938, signed by Britain, France, Germany, and Italy, ceded the Sudetenland to Germany over the objections of the Czechoslovak government. Germany then invaded Czechoslovakia on the 15th of March 1939 in violation of that same agreement. Each concession made the next demand easier to issue. On the 23rd of August 1939, Germany and the Soviet Union signed their non-aggression pact, including a secret protocol for dividing Poland. Two days later, Britain signed a military alliance with Poland. The stage was set, and the prewar architecture for preventing conflict had collapsed entirely.
Germany invaded Poland on the 1st of September 1939, and Britain and France declared war on Germany two days later. Australia, New Zealand, South Africa, and Canada declared war within the following two weeks. The Soviet Union invaded Poland from the east on the 17th of September but remained officially neutral between Germany and the western allies. Italy remained neutral until it declared war on Britain and France on the 10th of June 1940. As Germany rapidly overran Denmark, Norway, the Low Countries, and France in April and May of 1940, the governments of those occupied countries fled to London. Britain recognized Charles de Gaulle as the leader of the Free French forces, though the Free French were not recognized as a government-in-exile until 1944. The First Inter-Allied Meeting in London in early June 1941 brought together the United Kingdom, the four allied British Dominions, eight governments-in-exile, and Free France. That meeting produced the Declaration of St James's Palace, committing all signatories to work together until victory was achieved and an enduring peace secured. On the 22nd of June 1941, Hitler broke the non-aggression agreement with Stalin, and Axis forces invaded the Soviet Union. Britain formed an alliance with the Soviet Union the following month. The Atlantic Conference in August 1941 between President Franklin Roosevelt and Prime Minister Winston Churchill defined a shared Anglo-American vision for the postwar world, which was formalized as the Atlantic Charter. On the 7th and the 8th of December 1941, Japan attacked American and British territories across Asia and the Pacific, bringing the United States into the war as an Allied power. China, which had been resisting Japanese invasion since 1937 following the Marco Polo Bridge incident, formally declared war on the Axis on the 9th of December.
Winston Churchill called the partnership of the United Kingdom, United States, Soviet Union, and other Allies the "Grand Alliance". The "Big Three" , the United Kingdom, the United States, and the Soviet Union , were the principal contributors of manpower, resources, and strategy. The United States additionally regarded China and its leader Chiang Kai-shek as its main ally in Asia, elevating China to the status of a fourth major power, a view not consistently shared by the United Kingdom and Soviet Union. In December 1941, at the First Washington Conference, Roosevelt proposed the name "United Nations" for the Allies and Churchill agreed. The Declaration by United Nations, signed on the 1st of January 1942, was signed first by Roosevelt, Churchill, and representatives of the Soviet Union and China, followed the next day by representatives of 22 other allied countries. The Free French were not invited to sign because the United States still recognized the Vichy government in France. France's provisional government eventually signed the declaration on the 26th of December 1944. After the declaration, countries that adopted it were considered Allies. The four major powers were also referred to as the "trusteeship of the powerful" and later as the "Four Policemen" of the United Nations. That framing pointed directly toward the postwar international order and the permanent membership structure of the UN Security Council.
Churchill and Roosevelt at the first Washington Conference in late 1941 and early 1942 agreed to prioritize the European and North African theatres and established the Combined Chiefs of Staff Committee. At Casablanca in January 1943, they decided on an invasion of Sicily and postponed a full landing in France until May 1944. At the Cairo Conference in November 1943, Churchill, Roosevelt, and Chiang Kai-shek discussed operations against Japan and issued the Cairo Declaration, which stated that Japan would lose all territories it had gained since 1914. Stalin declined to attend because the Soviet Union was not yet at war with Japan. At Tehran in November and December of 1943, the Big Three leaders met for the first time. They confirmed that a full-scale offensive in France in mid-1944 was the Allied priority, and Stalin announced he would declare war on Japan once Hitler was defeated. At the Yalta Conference in February 1945, Churchill, Roosevelt, and Stalin agreed on zones of occupation for a soon-to-be-defeated Germany and made plans for a postwar European settlement. The final summit of the Big Three saw new faces: Harry S. Truman and Clement Attlee represented the United States and United Kingdom at Potsdam in July and August of 1945, where they discussed the final operations against Japan and issued a demand for its unconditional surrender.
Relations between the United Kingdom and the United States were especially close, reinforced through the destroyers-for-bases deal in September 1940 and the Lend-Lease program from March 1941. The British Commonwealth and empire obtained about half of the $42 to $50 billion in total Lend-Lease aid. The United States supplied the Soviet Union with $10 billion worth of aid under Lend-Lease, equivalent to approximately 7 percent of Soviet war production. The Soviet Union, in turn, bore the heaviest ground burden: an estimated 5 million Axis soldiers were killed or missing on the eastern front. Tensions surfaced repeatedly. American planners pushed for a landing in France in 1942 followed by a full invasion in 1943. Britain resisted, arguing an early landing risked being repulsed with heavy losses, and instead advocated wearing Germany down through strategic bombing and by opening fronts in North Africa, Italy, and the Balkans. Stalin was angered by the repeated postponements of an invasion of France, as the Soviet Union sustained severe losses. A rift developed over postwar Europe. The Soviet Union pressed Britain and the United States to recognize territorial gains it had made in the Baltic states, Finland, Bessarabia, and eastern Poland before the German invasion. The western allies rejected those demands as incompatible with the Atlantic Charter principle that territorial changes required the consent of the people concerned. Churchill and Stalin nonetheless reached a private agreement in October 1944 dividing spheres of influence across Romania, Bulgaria, Yugoslavia, Hungary, and Greece. On the 8th of August 1945, six days before Japan's surrender, the Soviet Union honored its commitment and entered the war against Japan.
Brazil was the only South American country to send troops to the European theatre, dispatching a 25,700-strong Expeditionary Force that fought mainly on the Italian front from September 1944 to May 1945. On the 15th of May 1943, the Cuban patrol boat CS-13 sank the German submarine U-176. The Dominican Republic stood apart by offering to accept up to 100,000 Jewish refugees at the Evian Conference, ultimately settling a community of around 700 European Jews in Sosua on the country's northern coast. Mexico declared war on the Axis in 1942 after German submarines sank its oil tankers Potrero del Llano and Faja de Oro, and it went on to form the Escuadron 201 fighter squadron, which carried out tactical air support missions during the liberation of Luzon in the summer of 1945. Norway's merchant fleet, then the fourth largest in the world, was organized into Nortraship, which at its height operated more than 1,000 ships in service of the Allied cause. The Belgian Congo's uranium deposits contributed to the Allied effort to develop the atomic bomb. India fielded 2.5 million soldiers by 1945, described as the largest volunteer army in history, while an estimated 3 million Indian people died in the Bengal famine of 1943. Poland, which had started the war fielding the third-largest army among the European Allies after the Soviet Union and the United Kingdom, saw its government-in-exile field 83,000 troops as the II Corps, which later fought in Italy after evacuation from the Soviet Union in mid-1942.
After the war ended, the Declaration by United Nations and the alliance it had formalized became the foundation of the modern United Nations. The process of building that successor institution was itself a product of wartime diplomacy. At Tehran, Roosevelt had outlined his vision of China as one of the "four policemen" of the postwar world. The Four Power Declaration of October 1943, signed by the United States, the United Kingdom, the Soviet Union, and China, had already pledged those nations to cooperate after the war and establish an international organization for peace and security. At Yalta, plans for the new United Nations organization were among the agreements reached. The Big Four powers were preparing to invite signatories to the San Francisco Conference to draft a charter for the new organization when eleven nations adhered to the Declaration by United Nations in early 1945. The alliance that had assembled from a desperate starting position in September 1939 had, by its end, produced both a military victory and a blueprint for the international order that followed.
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Common questions
When was the Allied coalition of World War II formally established?
The Allies were formally established as a named group on the 1st of January 1942, when 26 countries signed the Declaration by United Nations. The United States, the United Kingdom, the Soviet Union, and China signed first, followed by representatives of 22 other allied countries the next day.
Who were the Big Four Allied powers in World War II?
The Big Four were the United Kingdom, the United States, the Soviet Union, and China. The Declaration by United Nations officially recognized them as the "Four Powers," and they were also referred to as the "Four Policemen" of the United Nations.
When did the United States officially join the Allies in World War II?
The United States officially joined the Allies after Japan attacked American and British territories on the 7th and the 8th of December 1941. On the 8th of December, the US Congress declared war on Japan at the request of President Franklin D. Roosevelt, and Germany and Italy declared war on the United States on the 11th of December.
How much Lend-Lease aid did the Allies receive during World War II?
Total Lend-Lease aid amounted to $42 to $50 billion. The British Commonwealth and empire obtained about half of that total. The United States separately supplied the Soviet Union with $10 billion worth of aid, equivalent to approximately 7 percent of Soviet war production.
What was the Declaration by United Nations in World War II?
The Declaration by United Nations was a formal agreement signed on the 1st of January 1942 by 26 countries pledging to oppose the Axis powers and not negotiate a separate peace. Countries that subsequently adopted the declaration were considered Allied members; the French provisional government signed on the 26th of December 1944, and eleven more nations adhered in early 1945.
What role did China play in the Allied coalition during World War II?
China had been at war with Japan since the Marco Polo Bridge incident of the 7th of July 1937 and formally declared war on the Axis on the 9th of December 1941. China committed more troops than any member outside the Big Three; more than 1.5 million Japanese troops were tied down in the China theatre, troops that otherwise could have been deployed elsewhere.
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