Invasion of Poland (1939)
Part of World War II
German battleship Schleswig-Holstein, shelling Westerplatte, September 1, 1939.
Date 1 September – 6 October 1939 Location Poland Result Decisive Axis and Soviet victory; Polish territory split between Germany and the USSR
Combatants
Poland	Germany Soviet Union Slovakia
Commanders
Edward Rydz-Śmigły	Fedor von Bock (Army Group North), Gerd von Rundstedt (Army Group South), Mikhail Kovalev (Belorussian Front), Semyon Timoshenko (Ukrainian Front), Ferdinand Čatloš (Field Army Bernolák)
Strength
Poland: 39 divisions, 16 brigades, 4,300 guns, 880 tanks, 400 aircraft Total: 950,000	Germany: 56 divisions, 4 brigades, 9,000 guns, 2,500 tanks, 2,315 aircraft Soviet Union: 33+ divisions, 11+ brigades, 4,959 guns, 4,736 tanks, 3,300 aircraft Slovakia: 3 divisions Total: 1,500,000 Germans, 800,000+ Soviets, 50,000 Slovaks Grand total: 2,350,000+
Casualties and losses
Poland: 66,000 dead, 133,700 wounded, 694,000 captured	Germany: 16,343 dead, 27,280 wounded, 320 missing Soviet Union: 737 dead or missing, 1,125 wounded Slovakia: 18 dead, 46 wounded, 11 missing

v • d • e Invasion of Poland

Westerplatte – Danzig – The Border - Krojanty – Chojnice – Grudziądz – Lasy Królewskie – Mokra – Gdańsk Bay – Pszczyna – Mława – Tuchola Forest – Jordanów – Borowa Góra – Mikołów – Węgierska Górka – Tomaszów Mazowiecki – Wizna – Łódź – Przemyśl – Piotrków – Różan – Radom – Łomża – Wola Cyrusowa – Warsaw – Gdynia – Hel – Bzura – Jarosław – Kałuszyn – Węgrów – Wilno – Lwów – Modlin – Kobryń – Brześć – Kępa Oksywska – Tomaszów Lubelski – Wólka Węglowa – Kampinos Forest – Janów, Wereszyca, and Hołosko – Krasnystaw – Grodno – Cześniki – Krasnobród – Władypol – Szack – Wytyczno – Parczew – Kock

v • d • e Campaigns & Theatres of World War II

Europe Poland – Phoney War – Finland  – Denmark & Norway France & Benelux – Britain – Eastern Front – North West Europe (1944–45) The Mediterranean, Africa and The Middle East Mediterranean Sea – East Africa – North Africa – West Africa  Balkans (1939–41) – Middle East – Yugoslavia – Madagascar – Italy Asia & The Pacific China – Pacific Ocean – South-East Asia  South West Pacific – Japan – Manchuria Other Campaigns Atlantic – Strategic Bombing – North America Contemporaneous Wars Chinese Civil – Soviet-Japanese Border – French-Thai - Anglo-Iraqi  Invasion of Iran – Greek Civil – Sino-Japanese – Ecuadorian-Peruvian

The Invasion of Poland, 1939 (in Poland also "the September Campaign," "Kampania wrześniowa," and "the 1939 Defensive War," "Wojna obronna 1939 roku"; in Germany, "the Poland Campaign," "Polenfeldzug," codenamed "Fall Weiss," "Case White," by the German General Staff, and sometimes called "the Polish-German War of 1939"), which precipitated World War II, was carried out by Nazi Germany, the Soviet Union and a small German-allied Slovak contingent.

The invasion of Poland marked the start of World War II in Europe as Poland's western allies, the United Kingdom, Australia and New Zealand, declared war on Germany on September 3, soon followed by France, South Africa and Canada, among others. The invasion of Poland began September 1, 1939, one week after the signing of the Molotov-Ribbentrop Pact, and ended October 6, 1939, with Germany and the Soviet Union occupying the entirety of Poland. Although the United Kingdom and France declared war on Germany soon after Germany attacked Poland, very little direct military action was rendered (see Phoney War and Western betrayal).

Following a German-staged "Polish attack" on August 31, 1939, on September 1, German forces invaded Poland from the north, south, and west. Spread thin defending their long borders, the Polish armies were soon forced to withdraw east. After the mid-September Polish defeat in the Battle of the Bzura, the Germans gained an undisputed advantage. Polish forces then began a withdrawal southeast, following a plan that called for a long defense in the Romanian bridgehead area where the Polish forces were to await an expected Allied counter-attack and relief.

On September 17, 1939, the Soviet Red Army invaded the eastern regions of Poland in cooperation with Germany. The Soviets were carrying out their part of the secret appendix of the Molotov-Ribbentrop Pact, which divided Eastern Europe into Nazi and Soviet spheres of influence. Facing the second front, the Polish government decided the defense of the Romanian bridgehead was no longer feasible and ordered the evacuation of all troops to neutral Romania. By October 1, Germany and the Soviet Union had completely overrun Poland, although the Polish government never surrendered. In addition, Poland's remaining land and air forces were evacuated to neighboring Romania and Hungary. Many of the exiles subsequently joined the recreated Polish Army in allied France, French-mandated Syria, and the United Kingdom.

In the aftermath of the September Campaign, a resistance movement was formed. Poland's fighting forces continued to contribute to Allied military operations and did so throughout the duration of World War II. Germany captured the Soviet-occupied areas of Poland when it invaded the Soviet Union on June 22, 1941, and lost the territory in 1944 to an advancing Red Army. Over the course of the war, Poland lost over 20% of its pre-war population under an occupation that marked the end of the Second Polish Republic.

Opposing forces

Main article: Opposing forces in the Polish September Campaign

Germany

Germany had a substantial numerical advantage over the Polish and had developed a significant military prior to the conflict. The Heer (Army) had some 2,400 tanks organized into six panzer divisions, utilizing a new operational doctrine. It held that these divisions should act in coordination with other elements of the military, punching holes in the enemy line and isolating selected enemy units which would be encircled and destroyed. This would be repeated and followed up by less mobile mechanized infantry and foot soldiers. The Luftwaffe (Air Force) provided both tactical and strategic air power, particularly dive bombers that attacked and disrupted the enemy's supply and communications lines. Together the new operational methods were nicknamed Blitzkrieg (lightning war). Historian Basil Liddell Hart and A. J. P. Taylor conclude "Poland was a full demonstration of the Blitzkrieg theory".

Aircraft played a major role in the campaign. Bomber aircraft also attacked cities, causing huge losses amongst the civilian population through terror bombing. The Luftwaffe forces consisted of 1,180 fighter aircraft: 290 Ju 87 Stuka dive bombers, 1,100 conventional bombers (mainly of the He 111 and Dornier Do 17 type), and an assortment of 550 transport and 350 reconnaissance aircraft. In total, Germany had close to 4,000 aircraft, all up to modern standards. A force of 2,315 aircraft were assigned to Weiss. Due to its participation in the Spanish Civil War, the Luftwaffe was probably the most experienced, best trained and well equipped air force in the world in 1939.

Poland

Between 1936 and 1939, Poland invested heavily in industrialization in the Central Industrial Region. Preparations for a defensive war with Germany were ongoing for many years, but most plans assumed fighting would not begin before 1942. To raise funds for industrial development, Poland sold much of the modern equipment it produced. In 1936, a National Defence Fund was set up collect funds necessary for improving the fighting ability of the Polish Armed forces. The Polish Army had approximately a million soldiers, but less than half of them were mobilized by September 1. Latecomers sustained significant casualties when public transport became targets of the Luftwaffe. The Polish military had fewer armoured forces than the Germans, and these units, being dispersed within the infantry, were unable to effectively engage the enemy.

Experiences in the Polish-Soviet War shaped Polish Army organisational and operational doctrine. Unlike the trench warfare of the First World War, the Polish-Soviet War was a conflict in which the cavalry's mobility played a decisive role. Poland acknowledged the benefits of mobility but was unwilling to invest heavily in many of the expensive, unproven inventions since then and to make these additions to its armed forces. In spite of this, Polish Cavalry brigades were used as a mobile mounted infantry and had some successes against both German infantry and German cavalry.

The Polish Air Force (Lotnictwo Wojskowe) was at a severe disadvantage against the German Luftwaffe although it was not destroyed on the ground. The Polish Air Force lacked modern fighter aircraft, but its pilots were among the world's best trained, as proven a year later in the Battle of Britain, in which the Poles played a major part in beating the Luftwaffe.

Overall, the Germans enjoyed numerical and qualitative aircraft superiority. Poland had only approximately 600 modern aircraft. The Polish Air Force had approximately 185 PZL P.11 and some 95 PZL P.7 fighters, 175 PZL.23 Karaś B, 35 Karaś A, and by September over 100 PZL.37 Łoś were produced. Additionally there were over a thousand obsolete transport, reconnaissance and training aircraft. However for the September Campaign only some 70% those aircraft were mobilised. Only 36 PZL.37 Łoś bomber aircraft were deployed for action. All those aircraft were of indigenous Polish design, with the bombers being more modern than fighters according to the Ludomil Rayski air force expansion plan relying on the strong bomber force. Polish fighter aircraft were a generation older than their German counterparts. The Polish PZL P.11 fighter, produced in the early 1930s, was capable of only 365 km/h (approximately 220 mi/hr), far less than German bombers; to compensate, the pilots relied on the P-11 maneuvrability and high diving speed.

The Polish Navy was a small fleet comprising of destroyers, submarines and smaller support vessels. Most Polish surface units followed Operation Peking, leaving Polish ports on August 20 and escaping to the North Sea to join with the British Royal Navy. Submarine forces participated in Operation Worek, with the goal of engaging and damaging German shipping in the Baltic Sea, but they had much less success. In addition, many Polish Merchant Marine ships joined the British merchant fleet and took part in wartime convoys.

The tank force consisted of two armoured brigades, four independent tank battalions and some 30 companies of TKS tankettes attached to infantry divisions and cavalry brigades.

Soviet Union

For more details on this topic, see Soviet order of battle for invasion of Poland in 1939.

Slovakia

For more details on this topic, see Slovak invasion of Poland.

Order of battle

Prelude to the campaign

Main article: Causes of World War II

The Nazi Party, led by Adolf Hitler, took power in Germany in 1933. At first, Hitler pursued a policy of rapprochement with Poland, culminating in the German-Polish Non-Aggression Pact of 1934. Early foreign policy worked to maneuver Poland into the Anti-Comintern Pact, forming a cooperative front against the Soviet Union. Germany sought to grab hold of Soviet territory, acquire Lebensraum and expand Großdeutschland. Poland would be granted territory of its own, to its northeast, but the concessions the Poles were expected to make meant that their homeland would become largely dependant on Germany, functioning as little more than a client state. Some felt Polish independence would eventually be threatened altogether.

In addition to Soviet territory, the Nazis were also interested in establishing a new border with Poland because the German exclave of East Prussia was separated from the rest of the Reich by the "Polish Corridor." Many Germans also wanted to incorporate the Free City of Danzig into Germany. While Danzig had a predominantly German population, the Corridor constituted land long disputed between Poland and Germany. After the Treaty of Versailles, Poland acquired the Corridor and this led to shifts in the region's population. Hitler sought to reverse this trend and made an appeal to German nationalism, promising to "liberate" the Germans still in the Corridor, as well as Danzig, since the port city was under the control of the League of Nations.

Poland participated in the partition of Czechoslovakia that followed the Munich Agreement as it coerced Czechoslovakia to surrender the city of Český Těšín by issuing an ultimatum to that effect on September 30, which was accepted by Czechoslovakia on the first of October.

In 1938, Germany began to increase its demands for Danzig while proposing that a roadway be built in order to connect East Prussia with Germany proper, running through the Polish Corridor. Poland rejected this proposal, fearing that after accepting these demands, it would become increasingly subject to the will of Germany and eventually lose independence as the Czechs had. The Poles also distrusted Hitler and his intentions. At the same time, Germany's collaboration with anti-Polish Ukrainian nationalists from the Organization of Ukrainian Nationalists further weakened German credibility in Polish eyes, which was seen as an effort to isolate and weaken Poland. The British were also aware of this. On March 30, Poland was backed by a guarantee from Britain and France, though neither country was willing to pledge military support in Poland's defense. British Prime Minister Neville Chamberlain and his Foreign Secretary, Lord Halifax, still hoped to strike a deal with Hitler regarding the Free City of Danzig (and possibly the Polish Corridor), and Hitler hoped for the same. By again resorting to appeasement, Chamberlain and his supporters believed war could be avoided and hoped Germany would agree to leave the rest of Poland alone. German hegemony over Central Europe was also at stake.

With tensions mounting, Germany turned to aggressive diplomacy. On April 28, 1939, it unilaterally withdrew from both the German-Polish Non-Aggression Pact of 1934 and the London Naval Agreement of 1935. In early 1939, Hitler had already issued orders to prepare for a possible "solution of the Polish problem by military means." Another crucial step towards war was the surprise signing of the Molotov-Ribbentrop Pact on August 23, the denouement of secret Nazi-Soviet talks held in Moscow which capitalized on France and Britain's own failure to secure an alliance with the Soviet Union. As a result, Germany neutralized the possibility of Soviet opposition in a potential campaign against Poland. In a secret protocol of this pact, the Germans and the Soviets agreed to divide Eastern Europe, including Poland, into two spheres of influence; the western third of the country was to go to Germany and the eastern two-thirds to the Soviet Union.

The German assault was originally scheduled to begin at 04:00 on August 26. However, on August 25, the Polish-British Common Defence Pact was signed as an annex to the Franco-Polish Military Alliance. In this accord, Britain had committed itself to the defence of Poland, guaranteeing to preserve Polish independence. At the same time, the British and the Poles were hinting to Berlin that they were willing to resume discussions - not at all how Hitler hoped to frame the conflict. Thus, he wavered and postponed his attack until September 1, managing to halt the entire invasion "in mid-leap", with the exception of a few units that were outside communication lines, towards the south (the Nazi press announced that fanatical Slovakians were behind the cross border raid).

On August 26, Hitler tried to dissuade the British and the French from interfering in the conflict, even pledging that the Wehrmacht forces would be made available to Britain's Empire in the future. In any case, the negotiations convinced Hitler that there was little chance the Western Allies would declare war on Germany, and even if they did, because of the lack of territorial guarantees to Poland, they would be willing to negotiate a compromise favourable to Germany after its conquest of Poland. Meanwhile, the number of increased overflights by high-altitude reconnaissance aircraft and cross border troop movements signalled that war was imminent.

On August 29, prompted by the British, Germany issued one last diplomatic offer, with Case White yet to be rescheduled. At midnight on August 29, German Foreign Minister Joachim von Ribbentrop handed British Ambassador Sir Neville Henderson the list of terms which would allegedly ensure peace in regards to Poland. Danzig was to return to Germany (Gdynia would remain with Poland), and there was to be a plebiscite in the Polish Corridor, based on residency in 1919, within the year. An exchange of minority populations between the two countries was proposed. A Polish plenipotentiary, with full powers, was to arrive in Berlin and accept these terms by noon the next day. The British Cabinet viewed the terms as "reasonable," except the demand for the urgent plenipotentiary, a form of ultimatum. When Polish Ambassador Lipski went to see Ribbentrop on August 30, he announced that he did not have the full power to sign, and Ribbentrop dismissed him. It was then broadcasted that Poland had rejected Germany's offer, and negotiations with Poland came to an end.

On August 30, the Polish Navy sent its destroyer flotilla to Britain executing Operation Peking. On the same day, Marshal of Poland Edward Rydz-Śmigły announced mobilization of Polish troops. However, he was pressured into revoking the order by the French, who apparently still hoped for a diplomatic settlement, failing to realize that the Germans were fully mobilized and concentrated at the Polish border. During the night of August 31 the Gleiwitz incident ("Polish" attack on the radio station) was staged near the German border city of Gleiwitz, in Upper Silesia. On August 31, 1939, Hitler ordered hostilities against Poland to start at 4:45 the next morning. Because of the prior discontinuation, Poland managed to mobilise only 70% of its planned forces, and many units were still forming or moving to their designated frontline positions.

Details of the campaign

Plans

German plan

The German plan Fall Weiss, for what became known as the September Campaign, was created by General Franz Halder, chief of the general staff, and directed by General Walther von Brauchitsch, the commander in chief of the upcoming campaign. The plan called for the start of hostilities before the declaration of war, which pursued a traditional doctrine of mass encirclement and the destruction of enemy forces. Germany's material advantages, including the use of modern airpower and tanks, were to be of great advantage. The infantry - far from completely mechanized but fitted with fast moving artillery and logistic support - was to be supported by German tanks and small numbers of truck-mounted infantry (the Schützen regiments, forerunners of the panzergrenadiers) to assist the rapid movement of troops and concentrate on localized parts of the enemy front, eventually isolating segments of the enemy, surrounding, and destroying them. The pre-war armored idea (which an American journalist in 1939 dubbed Blitzkrieg), which was advocated by some generals including Heinz Guderian, would have had the armor blasting holes in the enemy's front and ranging deep into the enemy's rear areas, but in actuality, the campaign in Poland would be fought along more traditional lines. This stemmed from conservatism on the part of the German high command, who mainly restricted the role of armor and mechanized forces to supporting the conventional infantry divisions.

Poland was a country well suited for mobile operations when the weather cooperated - a country of flat plains with long frontiers totalling almost 5,600 kilometres (3,500 mi), Poland had long borders with Germany on the west and north (facing East Prussia) of 2,000 kilometres (1,250 mi). Those had been extended by another 300 kilometres (180 mi) on the southern side in the aftermath of the Munich Agreement of 1938; the German incorporation of Bohemia and Moravia and creation of the German puppet state of Slovakia meant that Poland's southern flank was exposed to invasion.

German planners intended to fully utilise their advantageously long border with the great enveloping manoeuvre of Fall Weiss. German units were to invade Poland from three directions:

• A main attack from the German mainland through the western Polish border. This was to be carried out by Army Group South commanded by General Gerd von Rundstedt, attacking from German Silesia and from the Moravian and Slovak border: General Johannes Blaskowitz's 8th Army was to drive eastward against Łódź; General Wilhelm List's 14th Army was to push on toward Kraków and to turn the Poles' Carpathian flank; and General Walter von Reichenau's 10th Army, in the centre with Army Group South's armour, was to deliver the decisive blow with a northestward thrust into the heart of Poland.
• A second route of attack from the northern Prussian area. General Fedor von Bock commanded Army Group North comprising General Georg von Küchler's 3rd Army, which struck southward from East Prussia, and General Günther von Kluge's 4th Army, which struck eastward across the base of the Polish Corridor.
• A tertiary attack by part of Army Group South's allied Slovak units from the territory of Slovakia.
• From within Poland the German minority would assist in the assault on Poland by engaging in diversion and sabotage operations through Selbstschutz units prepared before the war.

All three assaults were to converge on Warsaw, while the main Polish army was to be encircled and destroyed west of the Vistula. Fall Weiss was initiated on September 1, 1939, and was the first operation of the Second World War in Europe.

Polish plan

The Polish defense plan, Zachód (West), was shaped by political determination to deploy forces directly at the German-Polish border, based upon London's promise to come to Warsaw's military aid in the event of invasion. Moreover, wi