On 1 September 1939, Germany invaded Poland; two days later Britain and France declared war on Germany. Roughly two weeks after Germany's attack, the Soviet Union invaded Poland from the east. Britain and France established the Anglo-French Supreme War Council to coordinate military decisions. A Polish government-in-exile was set up in London, joined by hundreds of thousands of Polish soldiers, which would remain an Allied nation until the end. After a quiet winter, Germany began its invasion of Western Europe in April 1940, quickly defeating Denmark, Norway, Belgium, the Netherlands, and France; all the occupied nations would subsequently establish a government-in-exile in London, with each contributing a contingent of escaped troops. Nevertheless, by roughly one year since Germany's violation of the Munich Agreement, Britain and its Empire stood alone against Hitler and Mussolini.