During World War 2, Britain was involved in a war against several countries. The main enemies were Germany, Italy and Japan.
Germany
Britain and Germany were at war from 1939 to 1945. The war began when Germany invaded Poland on September 1, 1939. Britain and France declared war on Germany two days later. The British Empire played a major role in the war, providing significant manpower, resources, and financial aid.
Italy
Italy entered the war in 1940, when Mussolini declared war on France and Britain. Italy's involvement was largely based on its desire to expand its territory and increase its power in Europe and North Africa.
Japan
Britain was also involved in a war with Japan from 1941 to 1945. The war began when Japan attacked the British naval base at Pearl Harbor in Hawaii on December 7, 1941. The attack on Pearl Harbor led to the United States entering the war, which significantly changed the course of the conflict.
The war ended on September 2, 1945, when Japan surrendered after the US dropped an atomic bomb on Hiroshima and Nagasaki.