Two days after German troops crossed into Poland, Neville Chamberlain announced in a somber BBC broadcast that Britain was at war with Germany. France followed hours later. The declaration ended a decade of appeasement policy and thrust Europe into a conflict that would kill an estimated 70 to 85 million people worldwide over the next six years.
Neville Chamberlain's voice cracked slightly as he addressed the nation at 11:15 a.m., informing listeners that no assurance had been received from Berlin that German forces would withdraw from Poland, and that consequently "this country is at war with Germany." Within minutes of the broadcast ending, air raid sirens wailed across London — a false alarm, but a chilling preview of what was to come.
The declaration was the culmination of a policy that had failed spectacularly. Chamberlain had returned from Munich a year earlier promising "peace for our time." Instead, Hitler had annexed the Sudetenland, swallowed the rest of Czechoslovakia, and then invaded Poland on September 1. France declared war roughly six hours after Britain, at 5 p.m. Paris time.
Australia, New Zealand, and other Commonwealth nations soon followed suit. The ocean liner Athenia was torpedoed by a German U-boat that very evening, killing 117 people — the first British ship sunk in the war and a grim sign of the six years of carnage to follow.