E-mail this story to a friend. 1939: Britain and France declare war on Germany Britain and France are at war with Germany following the invasion of Poland two days ago.1939: Britain and France declare war on Germany.At 1115 BST the Prime Minister, Neville Chamberlain, announced the British deadline for the withdrawal of German troops from Poland had expired.-mail this story to a friend. 1939: Britain and France declare war on Germany Britain and France are at war with Germany following the invasion of Poland two days ago.