September 1939: The Invasion of Poland

September 1939: The Invasion of Poland

World War II Begins in Europe


Poland is a relatively large county in Eastern Europe famous for its natural resources and agricultural production, as well as its industrial output. Its shifting borders have caused it to be both an aggressor, and more recently, a victim of geography. During World War II, it was invaded by both the Soviet Union and Nazi Germany. Despite being drastically outmanned and outgunned on both sides, the Poles fiercely resisted the invasions for nearly a month—just ten days shorter than France resisted the German invasion of 1940. Throughout the war, Poland would be an epicenter of extreme violence, war crimes, death camps, and barbaric conflicts between neighbors up and down its eastern border. Its history in World War II remains simultaneously complex and nuanced. Yet, there can be no doubt that Poland demonstrated remarkable heroics throughout the war—militarily and through the more than 7,000 Polish civilians who risked their lives to save Jewish neighbors.


Learning Objectives

  • Understand the origins and background of the German-Soviet Division of Poland.
  • Understand the complex, brutal invasions of Poland by Nazi Germany and the Soviet Union in September 1939.


Key Terms / Key Concepts

Wehrmacht: German military during World War II

Molotov–Ribbentrop Pact: neutrality pact between Nazi Germany and the Soviet Union signed in Moscow on August 23, 1939

Invasions of Poland: during September of 1939, when Poland was invaded by Germany from the North, South, and West; and the Soviet Union from the East

Blitzkrieg: German “lightning war” strategy that is highly mobile, and simultaneously uses airplanes, army, artillery, and tanks to eliminate a target


The Molotov-Ribbentrop Pact


Background: Germany, the USSR, and their Mutual Desire for Poland


Since the re-establishment of Poland as a sovereign nation at the end of World War I, both Germany and Russia had contested its right to exist. Historically, Poland’s territory had belonged, in part, to Germany and Russia from the mid-1800s until the First World War. Rich in resources, both sides wanted to reclaim Poland.

In the 1930s, Hitler’s desire to expand “living space” for the German people increased. The Allies, time and again, appeased Hitler by allowing him to annex territories such as Austria and the Sudetenland. The British and French governments drew the line, though, at the idea of Germany annexing Polish territory. This, they declared would result in a war declaration on Germany.

Similarly, Russia also had kept its eye on Poland since the end of World War I. Stalin wished to expand his influence in Europe and reclaim territory he believed rightfully belonged to him. Like Hitler, he also saw Poland as a country rich in agriculture and natural resources that would help fuel the Soviet war effort.

The Poles were fiercely independent, democratic, Catholic, and historically resistant to Russian occupation of their lands. Tragically, neither Hitler nor Stalin felt anything but contempt for the Polish people. For Hitler, all Slavic people were lesser humans. “Brutish and backward,” they were one tier above the Jews in the Nazi racial hierarchy. They also stood in the way of Hitler’s dreams of a great German race that would occupy all of Europe. For Stalin, the Poles were historic enemies of Russia, despite shared cultural and linguistic ties. As a result, when Poland was invaded by Germany and the Soviet Union, the Polish people would become targets for mass-execution, arrests, forced labor, and victims of war crimes.


Signing of the Molotov-Ribbentrop Pact. Vyacheslav Molotov signs in the foreground. Directly behind him is Joachim von Ribbentrop who stands beside Josef Stalin, 1939.


Temporary Allies


The Molotov–Ribbentrop Pact was a neutrality pact between Nazi Germany and the Soviet Union signed in Moscow on August 23, 1939 by foreign ministers Joachim von Ribbentrop (Germany) and Vyacheslav Molotov (Russia), respectively. The pact clarified the spheres of interest between the two powers. It remained in force for nearly two years until the German government of Adolf Hitler launched an attack on the Soviet positions in Eastern Poland during Operation Barbarossa on June 22, 1941.

The clauses of the Nazi-Soviet Pact provided a written guarantee of non-belligerence by each party towards the other and a declared commitment that neither government would ally itself to or aid an enemy of the other party. In addition to stipulations of non-aggression, the treaty included a secret protocol that divided territories of Poland, Lithuania, Latvia, Estonia, Finland, and Romania into German and Soviet “spheres of influence,” anticipating “territorial and political rearrangements” of these countries.


Poland Invaded: September 1939


Wieluń is a quiet, unassuming town of a little more than 20,000 people in south-central Poland.  Around 5:00 a.m. on September 1, 1939, the Poles awoke to a horrible screaming sound: columns of diving German, Stuka aircraft. The screams followed with massive explosions and human screams, as victims were injured, caught fire, or killed. By the end of the bombing, over 150 civilians had perished; the town nearly destroyed. And, for the first time in military history, aircraft was used to terrorize and level a city; marking the start of World War II. By the end of September, nearly all of Western Poland had experienced the same type of aerial bombardment as Wieluń. The German Wehrmacht invaded not only by air, but also by land. This style of combat came to be known as a blitzkrieg.

Although comparatively small, the Polish army hastily formed a defense of the country. Drastically outmatched and outgunned, they could not withstand the German onslaught for long. Before their defeat, however, the Polish army put up a remarkable defense of their capital city, Warsaw. For over three weeks, they held-out against the Wehrmacht as attacks came by both air and land. By the end of September, the German air force (Luftwaffe) had dropped over 560 tons of bombs and 72 tons of firebombs on Warsaw. More than 25,000 civilians and 6,000 Polish soldiers had perished. The Germans did not stop with the bombing of cities and towns. Stuka aircraft strafed fleeing civilians, including elderly, women, and children. Polish men were frequently rounded-up and shot. Poland had historically had a very high Jewish population. During the initial invasion, the Jews were especially targeted and shot. Once Nazi occupation of Poland was completed, the Jews would be systematically rounded-up and forced into ghettoes, and later concentration or death camps.


Map showing the invasions of Poland, September 1939. Poland is in Yellow. Germany is gray, and Russia is red.



Some Poles fled east in fear of the German invasion, hoping to find refuge in the eastern portions of the country. Little did they suspect that there was not one, but two invasions of Poland. On September 17, 1939, the Soviet Union invaded Poland from the east. Much of the Polish resistance had been crushed by the German Wehrmacht. When the Red Army began its invasion, they were met by a nearly crippled Polish army, and a host of defenseless civilians. Instead of liberators, the Poles quickly discovered that the Soviet Red Army meant to occupy their country, also. Although initially less brutal than the Germans in their tactics, the Poles understood that they could not trust the Russians either.

Over the course of nearly two succeeding years, the Soviets arrested over 100,000 Poles for various, usually invented, charges. Most were deported to the brutal, Soviet gulags where they engaged in forced labor, received minimal rations and health care, and were exposed to savage winters. Another 8,000 Poles were executed. Tens of thousands more were forcibly drafted into the Red Army. Moreover, the Soviet NKVD (Secret Police/Military) tediously monitored Polish communications and activities.  Infamously in the spring of 1940, the Soviets rounded-up over 20,000 Polish officers and intelligentsia. They were executed, primarily in the Katyn Forest outside of Smolensk. The corpses were thrown into mass graves. First discovered by the Germans during the war, the Soviets vehemently denied they had murdered the Polish officers. Instead, they presented it as a German war crime. Only in the late 1990s and early 2000s did the truth of the Polish officers emerge.


Significance of the Invasions


Poland suffered disproportionately during the initial months of World War II. Little did the Poles, or Polish Jews, know that the terrors they had endured in 1939 would only worsen as the war progressed. And yet, while Poland was militarily defeated and occupied by the Nazis by the end of September, their underground resistance movement remained strong. They had a government in exile in London, and a growing group of resistance fighters and partisans who would from the legendary Polish home army: the Armia Krajowa.


Defenders of Warsaw, September 1939.


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