Germany's invasion of Poland on September 1, 1939, is generally regarded as the start of World War II.

Adolf Hitler was the leader of Nazi Germany from 1933 to 1945.

The Soviet Union and Germany signed the Molotov-Ribbentrop Pact in August 1939, agreeing to divide Poland and other Eastern European countries between them.

Winston Churchill served as Prime Minister of the United Kingdom from 1940 to 1945.

The United Kingdom declared war on Germany on September 3, 1939, two days after the invasion of Poland.

Isoroku Yamamoto was the commander-in-chief of the Imperial Japanese Navy during World War II.

The United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki in August 1945.

The Yalta Conference was held in February 1945 between the leaders of the United States, the United Kingdom, and the Soviet Union to discuss the postwar world order.

Japan surrendered on September 2, 1945, after the atomic bombings of Hiroshima and Nagasaki.

The estimated number of casualties in World War II is between 50 and 85 million.

The United Nations was established in 1945 to promote peace and security, and to prevent future wars.

The United States emerged as the dominant superpower after World War II.

The Cold War was a period of geopolitical tension between the United States and the Soviet Union and their respective allies that began after the Second World War.

The Soviet Union launched the first artificial satellite, Sputnik 1, into space in 1957.

Harry S. Truman was the U.S. president who initiated the Marshall Plan in 1948.