The Allies, led by the United Kingdom and until its defeat, France, were joined in the European theatre by the Soviet Union in June 1941 and by the United States in December 1941. In the Asia-Pacific theater, the Allies were led by the Republic of China, following the 1937 invasion of China by Japan, and the United States and the British Commonwealth, following the 1941-1942 Japanese attacks. The primary Allied belligerents included the U.S., Britain, France, USSR, Australia, Belgium, Brazil, Canada, China, Denmark, Greece, Netherlands, New Zealand, Norway, Poland, South Africa, and Yugoslavia.
Australia entered World War II shortly after the invasion of Poland, declaring war on Germany on
3 September 1939. By the end of the war almost a million Australians had served in the Australian armed forces and Australian military units had fought in Europe, North Africa, and the South-West Pacific.
Canada entered the conflict with a declaration of war on Germany on 10 September 1939 and encompassed major campaigns in Italy and Northern Europe. Canada was active in defending the shipping lanes in the North Atlantic and the Canadian Merchant Navy completed over 25,000 voyages across the Atlantic. Canadians were also active in the Pacific.
In mid-1937, following the Marco Polo Bridge Incident, Japan began a full invasion of China. Starting at Shanghai, the Japanese pushed Chinese forces back, capturing the capital Nanjing in December. 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.
On 18 June 1940, General Charles De Gaulle broadcasted an appeal on BBC radio for French men and women to join him and the British in the fight against Nazi Germany. The Free French forces were vital in the southern landing also playing an important role in Italy with the other allies.
In 1939, the Italians under Mussolini issue an ultimatum to the Greeks demanding they allow the Italian Army to cross into and occupy Greece. It is Greece's finest moment and the Greek response inspired the world. Not only was the Italian advance smashed, the Italians were expelled from Greece and driven back to Albania.
New Zealand was involved for all but three of the 2179 days of the war - a commitment on a par only with Britain and Australia. It was a war in which New Zealanders gave their greatest national effort and a war that New Zealanders fought globally, from Egypt, Italy and Greece to Japan and the Pacific.
The European theater of World War II opened with the German invasion of Poland on September 1, 1939. The Polish Army was quickly pushed back. After Poland had been overrun, a government-in-exile, an armed forces, and an intelligence service were established outside of Poland. These organisations contributed to the Allied effort throughout the war.
The United Kingdom, along with the British Empire's Crown colonies, including the British West Indies and British India, declared war on Nazi Germany in 1939, after the German invasion of Poland. Hostilities with Japan began in 1941, after it attacked British colonies in Asia.
United States of America
They came late to the ballgame by British standards, but they came to play. They were crude, crass and lacking in military finesse according to Montgomery and other Allied leaders, but they won many more times than they lost. They fought down there in the mud and the blood and the gore and got the job done.
On June 22, 1941, Germany invaded Russia, thereby beginning Operation Barbarossa. Soon following, Italy, Romania, Hungary, Slovakia, and Finland declared war. The Soviet Union suffered grievous casualties in the Second World War, which they called the Great Patriotic War.