What Caused World War 2?


Quick Answer

Historians do not have a general consensus on the exact starting point of World War II. The first formal declarations of war among the major powers involved were in 1937, when Japan and China went to war, and in 1939, when Germany invaded Poland.

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Full Answer

Japan's involvement in World War II had roots going back to its seizure of Chinese territory in 1931. Formal war between the two countries was not declared until 1937, however, touched off by a battle near the Marco Polo Bridge in Beijing.

Germany annexed Czechoslovakia and Austria without provoking a response from any other powers, but France and Britain declared formal war on Germany after Germany invaded Poland in 1939. The USSR initially aided Germany in capturing Poland, but Germany eventually turned on the USSR, leading to the Soviet entry into the war on the side of the Allied Powers. Japan's campaign against China eventually led to the entrance of the United States into the war when Japan attacked the U.S. Navy at Pearl Harbor in response to an oil embargo.

Some historians argue that World War II is simply an extension of World War I. Other prior contributing factors are Italy's invasion of Ethiopia in 1935 and the Spanish Civil War, which began in 1936.

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