Invasion of Poland

The invasion of Poland was the joint attack on the Republic of Poland by Nazi Germany, the Slovak Republic and the Soviet Union that opened World War II. It began on 1 September 1939, when German forces crossed the border after the Danzig crisis and one week after the Molotov-Ribbentrop Pact, and it widened on 17 September when the Red Army entered eastern Poland under that pact's secret protocol. The Polish army withdrew eastward toward a planned defence of the Romanian Bridgehead, was beaten at the Battle of the Bzura, and was overtaken by the Soviet advance. Fighting ended on 6 October 1939, when Germany and the Soviet Union divided the country between them, although Poland never formally surrendered. The United Kingdom and France declared war on Germany on 3 September, but their direct help to Poland was very limited.