On September 1, 1939, one week after the signing of the Molotov–Ribbentrop Pact, Nazi Germany invaded Poland, marking the beginning of World War II in Europe.
The Paris Peace Conference and ensuing Treaty of Versailles, signed in June 1919, formally established the newly-founded Republic of Poland as an independent and sovereign state. But Germany’s territorial losses following the Treaty of Versailles incited German revanchism and created unresolved problems, particularly on the status of the Free City of Danzig and of the Polish Corridor.
The Molotov-Ribbentrop Pact
Attending to these issues was part of Adolf Hitler’s political platform, and following the Anschluss of Austria in March 1938 and the conquest of Czechoslovakia in March 1939, the Nazi dictator was now determined to invade and occupy Poland, which had guarantees of French and British military support should it be attacked by Germany.
Adolf Hitler first had to neutralize the possibility that the Soviet Union would resist the invasion of its western neighbour, and in August 1939, secret negotiations led to the signing of a Treaty of Non-Aggression between the two powers, known as the Molotov–Ribbentrop Pact, which secretly carved up Poland and the rest of Central and Eastern Europe into respective Soviet and German “spheres of influence.”
Hitler then gave orders for the invasion to start on August 26, but news of the signing of a formal treaty of mutual assistance between Great Britain and Poland caused him to postpone the start of hostilities for a few days. At 12:40 PM on August 31, 1939, Hitler ordered hostilities against Poland to start the next morning.
Invasion of Poland
At 04:45, on September 1, the old German pre-dreadnought battleship Schleswig-Holstein opened fire on the Polish military transit depot at Westerplatte, in the Free City of Danzig. At the same time, German forces crossed the Polish border with Slovak military forces advancing alongside the Germans in northern Slovakia.
Three days later and after their ultimatum was ignored, France and Britain declared war on Germany, followed by Australia, New Zealand, South Africa and Canada. World War II had begun.
The German Luftwaffe gained air superiority early in the campaign and attacked a number of military and civilian targets, destroying communications and increasing the pace of the advance which overran Polish airstrips.
As the Wehrmacht advanced into Poland, Polish forces withdrew from their forward bases of operation close to the German border towards Warsaw and Lwów, awaiting expected support and relief from France and the United Kingdom. But in the end, their aid was very limited and the Allies provided no direct military support to Poland, outside of a cautious French probe into the Saarland.
On September 17, the Soviet Red Army invaded Eastern Poland, rendering the Polish plan of defence obsolete. Facing a second front, the Polish government ordered an emergency evacuation of all troops to neutral Romania.
By early October, German and Soviet forces had gained full control over Poland. The success of the invasion marked the end of the Second Republic, though Poland never formally surrendered. After an initial period of military administration, Germany directly annexed western Poland and the Free City of Danzig while Soviet Union incorporated its newly acquired areas into its constituent republics.
In the aftermath of the invasion, a collective of underground resistance organizations formed the Polish Underground State while many of the military exiles that managed to escape joined the Polish Armed Forces in the West, loyal to the Polish government-in-exile.
Persecution of Polish Jews by the German occupation authorities began immediately after the invasion, particularly in major urban areas. In the first year and a half, the Nazis confined themselves to stripping the Jews of their valuables and property for profit, herding them into makeshift ghettos, and forcing them into slave labor.
But the segregation of Jews in ghettos culminated in the policy of extermination the Nazis called the “Final Solution to the Jewish Question”, discussed by senior Nazi officials at the Wannsee Conference in Berlin in January 1942. All anti-Jewish measures were radicalized and, under the coordination of the SS and with directions from the highest leadership of the Nazi Party, killings were committed in Poland, Germany and throughout occupied Europe.
By mid-1942, victims were being deported from ghettos across Europe in sealed freight trains to the extermination camps of German-occupied Poland, designed exclusively for the rapid and secretive elimination of Polish and foreign Jews, but also of ethnic Poles, Soviet civilians and prisoners of war, the Roma, the handicapped, political and religious dissidents, and gay men.
The Nazi death camps in occupied Poland accounted for half the Jews killed. At Auschwitz the Jewish death toll was 960,000; Treblinka 870,000; Bełżec 600,000; Chełmno 320,000; Sobibór 250,000; and Majdanek 79,000.
Find out more about Central European history in our On this Day series.