When did Hitler's invasion of Poland occur in relation to World War II?

Hitler's invasion of Poland occurred on September 1, 1939, which marked the beginning of World War II. This action prompted Britain and France to declare war on Germany on September 3, 1939. Therefore, the correct contextual understanding is that the invasion was indeed after the broader context of rising tensions in Europe but is traditionally viewed as the start of the conflict itself.

The invasion cannot be classified as occurring "before" World War II, as it was the event that triggered the war. The Treaty of Versailles negotiations took place after World War I, between 1919 and 1920, and were aimed at settling the ramifications of that conflict, not related to the events leading up to World War II. Also, World War I concluded in 1918, making any significant actions or invasions related to World War II in the timeframe before that irrelevant to the question.

Recognition of the timeline is critical in understanding the origins of World War II, with Hitler's invasion of Poland serving as a definitive starting point for the hostilities that followed.