In March of 1939, the German military moved in to control the rest of Czechoslovakia. This was against the Munich agreement. Chamberlain realised that his attempts to control Hitler had failed. He started to get Britain ready for war, using the new factories that had been built. Many new weapons were built, including the Supermarine Spitfire (a fighter aircraft), and radar. When the Germans invaded Poland on 1st September 1939, the British and the French talked together and decided to declare war on Germany (tell Germany war had started). Chamberlain spoke on the radio, and told the British people that war had begun.