The German invasion of Poland began World War II

At 4:43 a.m. on September 1, 1939, the German battleship Schleswig-Holstein opened fire on the Polish garrison at Westerplatte, near Danzig. Within hours, Germany had thrown roughly 1.5 million men, some 2,750 tanks, and thousands of aircraft across the Polish border in a fast, mechanized assault that gave the world a new word: blitzkrieg.

The attack came without a declaration of war and on a false pretext, part of a staged set of “Polish” provocations meant to make the victim look like the aggressor.

Having guaranteed Poland’s borders, Britain and France declared war on Germany on September 3, 1939. Poland fought on but was squeezed from the east when the Soviet Union invaded on September 17, and the last organized resistance ended on October 6.

The campaign opened the deadliest conflict in human history, a war that would kill tens of millions before it ended six years later.