Question

What is the final event that starts World War II?

GPT-4o mini
The final event that is widely considered to have triggered the start of World War II was the invasion of Poland by Germany on September 1, 1939. This aggressive act followed a series of escalating tensions in Europe, including Germany's earlier expansion into Austria and the Sudetenland, and marked the definitive start of military hostilities in the conflict. In response to Germany's invasion, Britain and France declared war on Germany on September 3, 1939, formally beginning World War II.