Invasion of Poland

Between 1 September and 6 October 1939, Poland was attacked from the west, north and south by Nazi Germany and its client state Slovakia, and from the east by the Soviet Union, and was overrun and partitioned between the two great powers. The German assault, which brought British and French declarations of war two days later, is generally taken as the start of the Second World War in Europe.

Poland had regained independence in 1918 after more than a century of partition. The peace settlement gave it a corridor of mostly Polish-populated land to the Baltic, separating German East Prussia from the rest of Germany, and made the largely German city of Danzig a nominally independent Free City. After Adolf Hitler took power in 1933, he first courted Poland, signing a non-aggression pact in 1934, but from the late 1930s pressed for Danzig and a German road across the Corridor. Poland refused and on 31 March 1939 secured guarantees from Britain and France. Hitler renounced the 1934 pact in April and privately told his generals that the real goal was not Danzig but "living space" in the east.

The decisive step was the Molotov–Ribbentrop Pact, signed in Moscow on 24 August 1939, a week before the invasion. Publicly a non-aggression treaty, it contained a secret protocol dividing eastern Europe, Poland included, into German and Soviet spheres. Germany staged a series of fake incidents, most notoriously a mock Polish raid on the Gleiwitz radio station, to present its attack as self-defence.

At 4.45 a.m. on 1 September the old battleship Schleswig-Holstein opened fire on the Polish depot at Westerplatte in Danzig, while German aircraft bombed the town of Wieluń and troops crossed the border on three sides. Germany had a large advantage in tanks and aircraft, and its Luftwaffe quickly won control of the air. Poland, hindered by a mobilisation that had been delayed under Western pressure, had placed much of its army close to the long border to protect its western industrial regions. It was soon outflanked.

Britain and France declared war on 3 September but gave little practical help; a limited French advance into the Saar achieved nothing. Polish forces fell back towards Warsaw and the south-east. Their counter-attack on the Bzura river, west of Warsaw, between 9 and 19 September was the largest battle of the campaign, but ended in defeat under heavy air attack. Warsaw was besieged from 13 September and bombed relentlessly.

On 17 September, having settled its border war with Japan, the Soviet Union sent the Red Army, over 800,000 strong, into eastern Poland, claiming to protect Ukrainians and Belarusians. Polish plans to hold out in the south-east near the Romanian border collapsed. The government crossed into Romania and ordered troops to escape and regroup in France. Warsaw surrendered on 28 September, the Hel peninsula on 2 October, and the last field force capitulated after the Battle of Kock on 6 October. Poland never formally surrendered.

Around 65,000 Polish soldiers were killed and some 660,000 captured, about 420,000 of them by Germany and 240,000 by the Soviet Union; German military deaths were around 16,000. Tens of thousands of Polish soldiers escaped abroad to fight on. Civilian deaths are estimated at between about 100,000 and 200,000, mostly caused by German military action and terror. German soldiers and SS units massacred civilians in many towns, and killings of Polish and Jewish civilians during the campaign are often seen as the opening of the Holocaust.

Germany annexed western Poland and Danzig and ruled the rest as the General Government; the Soviet Union absorbed the east into its Belarusian and Ukrainian republics. Both occupations were brutal. The Soviets deported and killed many thousands, including the Polish officers murdered in the Katyn massacre, and German rule was marked by mass murder on a vast scale. A Polish underground state and a government-in-exile carried on resistance.

Our 1938 map shows the Second Polish Republic, labelled Poland, before the invasion, and the 1945 map shows the situation at the end of the war that the invasion began.