On a seemingly ordinary day, August 25, 1939, the German battleship Schleswig-Holstein, a relic from a bygone era of naval warfare, sailed into the port of Danzig (now Gdańsk, Poland). Officially, its presence was celebratory, marking the anniversary of Germany’s victory at the Battle of Tannenberg during World War I. Flags fluttered, and sailors in pristine white uniforms stood at attention, their brass buttons gleaming under the summer sun. However, beneath this veneer of commemoration lay a far more sinister motive. Concealed within the ship’s depths were over two hundred marines, poised for a calculated and unprovoked assault on Poland. In the pre-dawn gloom of September 1, 1939, the Schleswig-Holstein stealthily navigated the short distance from Danzig harbor to the Bend of Five Whistles, positioning itself across from Westerplatte, a small Polish military depot.
At precisely 4:43 a.m., the battleship unleashed its guns, shattering the morning calm and firing the first shots of what would become World War II. This act of aggression begs a critical question: Why Did Hitler Invade Poland? The answer is complex, rooted in Hitler’s long-held expansionist ambitions, racist ideology, and strategic calculations, all converging to make Poland the first domino in a war that would engulf the world.
Long before Adolf Hitler ascended to power in January 1933, his worldview, steeped in violence and racial supremacy, was laid bare in his autobiographical manifesto, Mein Kampf (My Struggle). He argued that Germany’s defeat in World War I was not due to military failings but rather a betrayal from within, a “stab in the back” orchestrated by Jews and communists. The Treaty of Versailles, imposed upon Germany after the war, was, in his eyes, a humiliating and unjust treaty that further crippled the nation. Hitler believed that Germany’s destiny as the purported “master race” (Herrenvolk) could only be fulfilled through Lebensraum, or “living space.” This concept, central to Nazi ideology, envisioned Germany’s eastward expansion into territories primarily inhabited by Slavic peoples, who were deemed racially inferior. By the summer of 1939, Hitler had already successfully annexed Austria, the Sudetenland, and the entirety of Czechoslovakia, each time facing minimal resistance from Western powers. Poland, strategically located and possessing territories coveted by Hitler, was to be his next target.
Adolf Hitler inspecting German troops during a parade in Poland, shortly after the invasion in September 1939. This image, taken from the German Federal Archives, depicts Hitler’s presence in occupied Polish territory, highlighting the swiftness of the German advance and the symbolic victory parade.
Diplomatic Maneuvering and the Pact with Stalin
By April 28, 1939, Hitler began to dismantle the existing diplomatic framework. He unilaterally withdrew from the German-Polish Non-Aggression Pact of 1934 and the London Naval Agreement, signaling his aggressive intentions towards Poland. Simultaneously, he received intelligence that crucial talks between France, Britain, and the Soviet Union, aimed at forging an anti-aggression pact, had stalled. Despite his deep-seated hatred and contempt for Bolshevism, Hitler recognized a strategic opportunity in the Soviet Union. He astutely moved to secure a pact with Stalin, a move that would neutralize the Soviet threat from his eastern flank and allow him to wage war against Poland without the dreaded prospect of a two-front war or Soviet intervention.
The result was the Molotov-Ribbentrop Pact, signed hastily on August 23, 1939, just days before the planned invasion of Poland. In its public clauses, the Soviet Union pledged to remain neutral in the event of a war between Germany and Poland, effectively ensuring the Soviets would not aid Britain or France should they intervene to defend Poland. However, the true significance and most sinister aspect of the Molotov-Ribbentrop Pact lay in its secret protocol. This clandestine agreement redrew the map of Eastern Europe, dividing spheres of influence between Nazi Germany and the Soviet Union. Bessarabia, Finland, Estonia, Latvia, and eastern Poland were designated as falling within Stalin’s sphere, while western Poland was conceded to Hitler. As historian Timothy Snyder chillingly observed, this pact revealed a shared objective: “the two regimes immediately found common ground in their mutual aspiration to destroy Poland.” Hitler viewed Poland as an “unreal creation” of the Treaty of Versailles, while Molotov echoed this sentiment, labeling it an “ugly offspring” of the post-WWI settlement. This convergence of expansionist desires and mutual disdain for Poland sealed its fate.
“Case White”: The Blueprint for Invasion and Annihilation
With his eastern border seemingly secured through the pact with the Soviet Union, Hitler issued the final orders to his military command to implement “Case White” (Fall Weiss), the meticulously planned invasion of Poland. In a chillingly explicit statement of intent, Hitler articulated his objectives: “expanding our living space in the east and making our food supply secure; to have sufficient food you must have sparsely settled areas. There is therefore no question of sparing Poland, and the decision is to attack Poland at the first opportunity. We cannot expect a repetition of Czechoslovakia. There will be fighting.” This was not to be a mere territorial grab; it was to be a war of conquest intertwined with racial annihilation.
In a pivotal speech delivered to his military commanders at Obersalzberg on August 22, 1939, just days before the invasion, Hitler unveiled the brutal nature of the impending conflict. He declared that the objective was the physical destruction of the enemy. Poles, regardless of gender or age, were to be treated with extreme ruthlessness. The campaign was to be conducted “with the greatest brutality and without mercy.” To execute this policy of extermination, the Einsatzgruppen—special action groups of the SS—and police battalions were formed. Their mandate was to systematically eliminate Poles deemed likely to resist German rule. Lists of prominent Polish citizens—intellectuals, clergy, political leaders, and members of the intelligentsia—were compiled, marking them for immediate capture and execution. Hitler’s vision extended beyond mere military occupation; cities like Warsaw were slated for “cleansing” of their Jewish populations, and the ethnic Polish population was to be reduced to a pool of slave laborers serving the German “master race.” This monstrous plan of colonization, predicated on extreme violence and mass murder, was a precursor to the unimaginable horrors that would unfold during the Holocaust and the establishment of extermination camps.
Manufacturing a Pretext: False Flag Operations
The military strategy for the invasion of Poland was devised by Hitler, with the operational details refined by General Franz Halder, Chief of the General Staff, and General Walther von Brauchitsch, Commander-in-Chief of the Army. Crucially, Hitler was determined to present Poland as the aggressor, to fabricate a casus belli that would justify the German invasion in the eyes of the world and, more importantly, the German populace. To achieve this, the SS was tasked with orchestrating a series of false-flag operations, designed to create the illusion of “Polish provocations” against Germany.
According to testimony provided by Sturmbannführer Alfred Naujocks at the Nuremberg Trials, Reinhard Heydrich and Heinrich “Gestapo” Müller orchestrated Operation Himmler. This clandestine operation aimed to make it appear as though Poland was initiating hostilities, thereby providing a fabricated justification for the impending German aggression. The most infamous of these staged incidents was the attack on a radio station in Gleiwitz (now Gliwice, Poland) on the night of August 31, 1939. Franciszek Honiok, a local Silesian German farmer known for his pro-Polish sympathies, was arrested by the Gestapo, drugged, and then brutally murdered. His body, dressed in a Polish uniform, was then taken to the Gleiwitz radio station. SS operatives, posing as Polish insurgents, stormed the station, broadcast an anti-German message in Polish, and left Honiok’s body as “evidence” of Polish aggression. This meticulously staged event, a complete fabrication from beginning to end, was swiftly exploited by Joseph Goebbels’s propaganda machine. Within hours, German media was disseminating fabricated stories of heinous Polish attacks on German soil. By the morning of September 1, 1939, Hitler was already citing the Gleiwitz incident as a key justification for the invasion of Poland, launched just hours later with the attack on Westerplatte.
Blitzkrieg Unleashed: The German Invasion of Poland
At dawn on September 1, 1939, German forces surged across the Polish border from three primary directions, initiating the invasion. Army Group South, under the command of Colonel General Gerd von Rundstedt, spearheaded the main assault from Silesia in the west. This force was further subdivided into General Johannes Blaskowitz’s 8th Army, advancing towards Łódź, General Wilhelm List’s 14th Army, directed towards Kraków, and General Walter von Reichenau’s thrust aimed at Warsaw. The second major axis of attack originated from Prussia, led by Colonel General Fedor von Bock and Army Group North. General Georg von Küchler’s 3rd Army pushed southward from East Prussia, while General Günther von Kluge’s 4th Army targeted the Polish Corridor, a strip of land separating East Prussia from the rest of Germany. A smaller contingent of Slovakian units also participated in the invasion from the south. Furthermore, the Germans anticipated support from a fifth column of Volksdeutsche, ethnic Germans residing in Poland who were sympathetic to the Nazi regime, hoping they would undermine Polish defenses from within.
The military disparity between the two sides was vast from the outset. Germany had amassed a formidable invasion force of approximately 1.5 million soldiers, supported by 2,750 tanks, 2,315 aircraft, and 9,000 artillery pieces. In contrast, Poland, theoretically possessing an army of one million men, faced significant challenges in mobilization. Many Polish units were unable to reach their designated positions before the German onslaught. Those who did were often equipped with outdated weaponry and possessed far less matériel, with only 4,300 guns, 210 tanks, 670 tankettes, and 800 aircraft. The Polish strategic plan hinged on concentrating their forces in the west to repel the initial German attacks, while simultaneously awaiting the anticipated intervention of their allies, France and Britain. Poland had signed a military alliance with both nations on March 31, 1939, and the Polish government believed their allies would not stand idly by while Poland was overrun. Tragically, this faith in Allied intervention proved to be misplaced.
Compounding Poland’s disadvantage was the German deployment of a revolutionary new form of warfare: Bewegungskrieg, or war of movement, soon to be known as Blitzkrieg (lightning war). Pioneered by figures like General Heinz Guderian, Blitzkrieg tactics emphasized the rapid and coordinated employment of tank divisions, closely supported by the Luftwaffe. These armored spearheads would punch deep holes in enemy lines, overwhelming the opposition through speed, shock, and concentrated firepower. Mechanized infantry and support units would then follow, consolidating gains and allowing the tank divisions to surge forward again, maintaining relentless momentum. The German military also leveraged innovative technological and logistical advantages, including the widespread use of methamphetamine (Pervitin) to enhance soldier endurance and combat effectiveness, enabling troops to fight for extended periods without rest.
Valiant Resistance and Brutal Reprisals: The Polish Defense
Despite being unprepared for the speed and ferocity of Blitzkrieg, the Polish military mounted a determined and often courageous defense. By September 3, von Rundstedt’s divisions had penetrated deep into southern Poland, von Kluge’s forces had reached the Vistula River, and von Reichenau’s troops were advancing towards Kielce. However, Polish units offered fierce resistance at numerous points, achieving localized successes. At Pułtusk, for example, Polish forces managed to capture a significant number of German tanks. Contrary to German propaganda narratives depicting Polish cavalry charging tanks with sabers, Polish cavalry brigades were equipped with modern weaponry, including bolt-action rifles, machine guns, and crucially, anti-tank rifles, providing them with considerable firepower. At the Battle of Mokra, the Wołyńska Cavalry Brigade inflicted heavy losses on the Germans, destroying over 50 tanks and causing an estimated 800 casualties, marking one of the few clear Polish victories of the campaign. The largest engagement of the September Campaign, the Battle of Bzura, saw Polish forces launch a counter-offensive against the flank of German units advancing towards Warsaw, pushing them back by approximately 20 kilometers. Despite these pockets of success, by September 19, Polish forces were increasingly encircled and suffering heavy losses; an estimated 20,000 Polish soldiers had already been killed. Winston Churchill, acknowledging the Polish bravery in the face of overwhelming odds, lauded their struggle as “an ever glorious struggle.” Surviving Polish troops retreated towards Warsaw to bolster the city’s defenses.
Another grim innovation employed by the Germans during the September Campaign was mass terror bombing. From the outset, civilian populations were deliberately targeted. Over one hundred and fifty Polish towns and villages were bombed in the first days of the invasion, with the small town of Wieluń being virtually obliterated on September 1. Warsaw became a primary target, marking the first instance of a major European capital being systematically bombed by an enemy air force. Despite relentless aerial bombardment and the rapid advance of German ground forces, Warsaw’s citizens and remaining military units mounted a tenacious defense. During the aerial defense of Warsaw between September 1–6, Polish anti-aircraft batteries managed to shoot down over 80 German bombers. In retaliation, on September 10, the Luftwaffe unleashed 17 consecutive bombing raids on the city. Simultaneously, German tanks were closing in, tightening the siege. Approximately 150,000 civilians, terrified but resolute, joined in the defense effort, feverishly digging anti-tank ditches and erecting barricades throughout the city.
Polish soldiers operating an anti-aircraft gun in Warsaw during the Siege of September 1939. This photo, sourced from Wikimedia Commons, captures the determined defense of Warsaw against relentless German aerial attacks. The image underscores the Polish military’s and civilian population’s resilience in the face of overwhelming force.
On September 8, German tanks encircled Warsaw, and the ground assault began in the southern districts of the city. Initially, Polish defenders managed to repel the Panzer attacks. The Germans renewed their assault on September 9, but Polish soldiers and civilian volunteers fought back fiercely, using Molotov cocktails and setting fuel ablaze on the streets, destroying dozens of German tanks and forcing another German retreat. Approximately 140,000 poorly equipped Polish soldiers and civilian volunteers defended Warsaw against a German force of 175,000, supported by 1,000 artillery pieces and 1,000 aircraft. Despite the overwhelming odds, on September 15, the Warsaw garrison successfully repelled three major German assaults. Frustrated by the unexpectedly fierce resistance, Hitler, on September 25, demanded the immediate surrender of Warsaw. That day, the Luftwaffe unleashed a devastating aerial bombardment, dropping an estimated 560 tons of high-explosive bombs and 72 tons of incendiary bombs on the city. Polish composer and Holocaust survivor Władysław Szpilman vividly recalled the terror of these raids: “The noise of explosions merged with the constant thunder of guns, penetrated by the boom of nose-diving aircraft like electric drills boring holes in iron.”
Adding to the horror of the indiscriminate bombing was the deliberate strafing of civilians by German aircraft. American filmmaker Julien Bryan, who arrived in Warsaw on September 7, documented the unfolding tragedy with extraordinary courage. His film, Siege, provides a harrowing and unforgettable record of his time in the besieged city. In one poignant and deeply disturbing scene, Bryan captured the moment when a Luftwaffe plane machine-gunned women working in a field. He recorded the heart-wrenching cries of a young girl cradling one of the dead women, her sister: “Oh, my beautiful sister! What have they done to you? … Please talk to me! Please, oh, please! What will become of me without you!” Bryan later recounted: “I threw my arm about her and held her tightly, trying to comfort her. She cried. So did I and the two Polish officers who were with me. What could we, or anyone else, say to this child?”
The Soviet Betrayal and the Fall of Poland
Despite the valiant and protracted Polish resistance, any lingering hope of holding out against the German onslaught was extinguished on September 17, 1939, when the Soviet Union invaded Poland from the east. This act of aggression was in direct accordance with the secret protocol of the Molotov-Ribbentrop Pact, which had assigned eastern Poland to the Soviet sphere of influence. The Soviet invasion force was massive, comprising over 450,000 troops, 4,736 tanks, and 3,300 aircraft. Already severely weakened and facing collapse under the relentless German assault, the Polish army was utterly unable to mount a defense against this second invasion from the east. Plans to establish a final defensive line in southeastern Poland, near the Romanian bridgehead, became instantly irrelevant.
Warsaw, after weeks of heroic resistance and facing utter devastation, finally surrendered on September 27, 1939. The final civilian death toll in the siege of Warsaw alone exceeded 20,000. Sporadic fighting continued as German and Soviet forces methodically suppressed remaining pockets of Polish resistance. On October 6, following the Polish defeat at the Battle of Kock, German and Soviet forces achieved complete military control over the conquered Polish territory. Although Poland never formally surrendered, this date marks the effective end of the Second Polish Republic. The Polish dream of independence, which had seemed so promising after World War I, was brutally crushed.
The invasion of Poland unleashed an era of unprecedented death and destruction, ushering in World War II and subjecting Poland to the horrors of two of the 20th century’s most brutal totalitarian regimes. In western Poland, under Nazi occupation, Hitler’s racial war intensified rapidly. SS units, Einsatzgruppen, and Wehrmacht soldiers unleashed a wave of terror and violence against the Polish elite and, with increasing ferocity, against Poland’s Jewish population, marking the early stages of the Holocaust. In eastern Poland, under Soviet occupation, over one million Poles were rounded up and deported to the Soviet Union, including approximately 20,000 Polish officers who were subsequently murdered by the Soviets in the Katyn Forest and other locations. Despite the devastation and occupation, Polish resistance persisted throughout the war. Over 100,000 Polish soldiers managed to escape and would continue to fight alongside the Allies on virtually every European front, from the Battle of Britain to Narvik and Monte Cassino. Many of those deported to the Soviet Union would later form the Polish Anders Army, eventually fighting with distinction under British command in the Middle East and Italy. Within occupied Poland, the Polish people established the largest underground resistance army in occupied Europe, making invaluable contributions to the Allied war effort through intelligence gathering, including crucial assistance in cracking the Enigma code, obtaining intelligence on the German V-2 rocket program, and alerting the West to the unfolding horrors of the Holocaust. Tragically, despite their immense sacrifices and unwavering fight for freedom, Poland was not liberated in 1945 but instead found itself under another form of totalitarian rule, forced to exchange Nazi occupation for Soviet domination. However, the Polish spirit of resistance remained unbroken, and the long struggle for true independence finally culminated in 1989 with the collapse of communism.
The story of the September Campaign of 1939 is a crucial chapter in 20th-century history. It serves as a stark reminder of the devastating consequences of unchecked aggression, racist ideology, and appeasement. Understanding why Hitler invaded Poland is not only essential to comprehending the origins of World War II but also to appreciating the enduring struggle for freedom and the profound resilience of the Polish people in the face of unimaginable adversity. The invasion of Poland was more than just a military campaign; it was the opening act of a global tragedy that reshaped the world.
