Why did the German ivasion of danzig provoke war?

The German invasion of Danzig in September 1939 provoked war primarily because it violated the Treaty of Versailles, which had established Danzig as a Free City and limited German expansion. The invasion was part of Adolf Hitler's broader strategy to reclaim territories lost after World War I and assert German dominance in Europe. Britain and France had pledged to defend Poland, and when Germany attacked, they declared war on Germany in response, marking the start of World War II. This act was seen as an aggressive expansion that threatened European stability, prompting the Allied nations to take action.