On September 3, 1939, Britain and France declared war on Germany in response to the German invasion of Poland two days earlier. Addressing Britons from 10 Downing Street 75 years ago today, Prime Minister Neville Chamberlain explained that the 11 a.m. deadline the British had set for Germany to begin withdrawing its troops from Poland had passed. "Consequently," Chamberlain announced at around 11:15 a.m. London time, "this country is at war with Germany." He then paused for almost 5 seconds, letting the crushing reality of those words sink in for his listeners.

In the three-minute announcement above, which the BBC carried that morning, Chamberlain sounded defeated, calling the declaration of war a result of his failure to make peace.

You can imagine what a bitter blow it is to me that all my long struggle to win peace has failed. Yet I cannot believe that there is anything more or anything different that I could have done and that would have been more successful.

Before calling on British citizens to assist in the war effort—"I know that you will all play your part with calmness and courage"—Chamberlain insisted: "We have a clear conscience. We have done all that any country could do to establish peace."

But, he said, "[t]he situation in which no word given by Germany's ruler could be trusted and no people or country could feel themselves safe has become intolerable."

In a follow-up announcement, BBC presenter Alvar Lidell instructed Britons to carry gas masks and stay off the streets, announcing that schools would be closed for at least a week. "People are earnestly requested not to crowd together unnecessarily for any purpose," Lidell said.