The British people had been aware of the threat of war for some time before war was actually declared on 3 September 1939. When Adolf Hitler and the Nazis had come into power in 1933, they'd started to reclaim the territories taken away from Germany after the First World War. In March 1938, German troops invaded Austria, and then Hitler demanded the Sudetenland: a part of Czechoslovakia that had never belonged to Germany in the first place. To try and avoid another war, the British Prime Minister, Neville Chamberlain, went to meet Hitler in Munich in September 1938, along with the French Prime Minister and the Italian dictator, Mussolini (Hitler's ally). The Sudetenland was handed over to Germany, against the wishes of the Czech government, with Hitler promising that he wouldn't claim any more land. The photograph below shows a Czech woman weeping as she gives the Nazi salute while German troops march into the Sudetenland.

Chamberlain came back to Britain saying that he'd achieved 'peace in our time'. He was to be proven wrong in March 1939, when Hitler and his army marched into Czechoslovakia to take over the whole country.

The Prime Minister's meeting with Hitler in 1938 came to be known as the Munich crisis, and many people believed then that war was only days away. Hundreds left London to stay with friends or family in the country, and some children were even sent away to relatives overseas. Evacuation plans (later called off) were put into place for all London schoolchildren to leave the city, sandbags started appearing outside municipal buildings for protection in the event of bombing raids, and trenches were dug in parks, in case people suddenly had to take shelter. In January 1939, the Air Raid Precautions (ARP) Act was passed. Now everyone started thinking about where to build air-raid shelters and how to black out their houses so that German bombers wouldn't be attracted by the tiniest chink of light. Gas masks were issued, ARP wardens started patrolling the streets, and boy scouts were recruited as messenger boys. When Hitler invaded Poland on 1 September 1939, Britain could no longer stand back - having previously promised with France to defend Poland if she was ever attacked.

Prime Minister Neville Chamberlain came on the wireless at 11.15 on the morning of Sunday 3 September to tell the British people their country was at war with Germany. By then, almost a million and a half children were in the process of being evacuated from cities to (supposedly) safe havens in the country. The photographs below show evacuees leaving the port of Gravesend in Kent (which everyone feared would be invaded) for their new homes, their gas masks in cardboard boxes around their necks.