In which year did World War II begin?

World War II began in 1939 when Germany invaded Poland on September 1st, marking the official start of the conflict in Europe. This invasion prompted Britain and France to declare war on Germany shortly thereafter, fundamentally altering the geopolitical landscape of the time. The significance of this date is underscored by the fact that it led to a global conflict involving numerous countries and military alliances, which would go on to shape the course of history through to the end of the war in 1945. Understanding the context of the invasion of Poland is crucial for grasping the origins of the war and its subsequent escalation.