Who started WW2?

World War II was primarily initiated by Germany's invasion of Poland on September 1, 1939. This aggressive act followed a series of expansionist policies and invasions by Nazi Germany under Adolf Hitler. In response to the invasion, Britain and France declared war on Germany on September 3, 1939, marking the official start of the conflict. While Germany played a central role, various other nations' actions and alliances also contributed to the war's escalation.