The beginning of World War II

On September 1, 1939, Nazi German forces, under the orders of Adolf Hitler, crossed the western and northern borders into Polish territory. The invasion of Poland marked the beginning of World War II—a war that, in the following days, with the entry of Britain and France into confrontation with Germany, expanded beyond a regional conflict.

German forces, employing a strategy known as "Blitzkrieg" (lightning war), launched coordinated ground and air attacks against Poland. Two days later, Britain and France declared war on Germany. World War II ultimately continued until 1945 and engulfed Europe, Asia, and vast parts of the world.