Invasion of Poland

On 1 September 1939 German forces invaded Poland from the west, south and north, while Slovak troops advanced from the south, opening the Second World War in Europe. Britain and France, bound by guarantees to Poland, declared war on Germany two days later, but their promised offensive in the west never came. The campaign introduced the world to blitzkrieg: massed panzers, motorised infantry and close air support broke through the frontier and raced for Warsaw, while the Luftwaffe struck cities and the Polish army, though numerous, was outflanked and encircled. Warsaw held out under bombardment until 28 September and surrendered, and organised resistance ended in early October. On 17 September the Soviet Union invaded from the east under the secret terms of the Molotov-Ribbentrop Pact, and Poland was partitioned between Germany and the USSR. Tens of thousands of Polish soldiers escaped abroad to continue the fight, and the occupation that followed would become one of the war most brutal. Poland fell in five weeks, but the war it began would last six years.