On 1 September 1939, Germany invaded Poland; two days later, Britain and France declared war on Germany, launching the Second World War. Within three weeks, the Red Army of the Soviet Union invaded the eastern regions of Poland in fulfilment of the secret Molotov-Ribbentrop Pact with Germany. A British Expeditionary Force (BEF) was sent to the Franco-Belgian border, but Britain and France did not take any direct action in support of the Poles. By 1 October, Poland had been completely overrun.