Military history of Poland during World War II

• 1. Introduction

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  Poland's military history during World War II opens with a jump far from Polish soil. Paratroopers of the 1st Independent Polish Parachute Brigade dropped into the Netherlands during the Battle of Arnhem, part of Operation Market Garden. Their homeland had already been divided between two invading armies, yet its government never signed a formal surrender. Forces raised abroad kept fighting under foreign command, while a resistance carried on inside occupied Poland. Together these forces made Poland the fourth largest Allied fighting force in Europe, behind only the Soviet Union, the United States and Britain. What let a defeated nation build an army this size on other countries' soil? What became of the intelligence network and underground state that kept operating after the government fled abroad? And what did it cost ordinary Poles to shelter their Jewish neighbors, under an occupation that punished that kind of help with death?

• 2. The September Defeat

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  On Friday the 1st of September 1939, Nazi Germany invaded the Second Polish Republic, opening the European campaign of World War II. Under the Molotov-Ribbentrop Pact's secret protocol, the Soviet Union invaded from the east on the 17th of September. Germany had urged the move once its own forces neared the agreed line of interest. The Soviets, caught off guard by how fast Germany advanced, had expected weeks to prepare rather than mere days, but still promised to move quickly. That Soviet thrust doomed Polish hopes of making a prolonged stand at the Romanian bridgehead. The last Polish Army units gave up the fight in early October, following defeat at the Battle of Kock. By the 6th of October, German and Soviet forces held all of Poland between them.

  On the 3rd of September, honoring their treaty commitments, the United Kingdom and France declared war on Germany. Hitler had gambled, wrongly, that Britain and France would let him annex Polish territory without a military response. The invasion began exactly one week after the pact's signing, a document whose secret protocol split Northern and Central Europe into German and Soviet spheres. Not every clash went Germany's way at first: Polish forces won the Battle of Mokra on the 1st of September, and the garrison at Westerplatte held out for roughly a week before it fell. Those bright spots could not offset the wider collapse, and defeats followed at Warsaw, the Bzura, Lwów and Wilno as September wore on.

  German losses in the campaign reached roughly 16,000 killed, 28,000 wounded and 3,500 missing, plus more than 200 aircraft and 30 percent of their armored vehicles destroyed. Polish casualties ran far heavier, at about 66,000 dead and 694,000 taken captive. Those German losses equaled half of everything Germany would suffer before it invaded the Soviet Union in 1941. A campaign lasting about a month burned through eight months' worth of German supplies. That drain on stockpiles would shape German planning for the fighting still ahead.

• 3. Saving Lives Under Occupation

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  In German-occupied Poland, anyone caught helping a Jew faced execution alongside their entire family, a punishment unique to that occupation in Europe. Despite that threat, Poland was also the only German-occupied country to build an organization aimed specifically at helping Jews. Known by the cryptonym Żegota, it supplied food, shelter, medical care, money and false identity papers. Most of its funding came directly from the Polish Government-in-Exile based in Great Britain.

  Most Jews who survived German-occupied Poland, however, were saved by Poles with no connection to Żegota at all. Estimates of Jewish survivors in Poland range between 40,000-50,000 on one count and 100,000-120,000 on another. Scholars estimate that saving the life of a single Polish Jew typically took the sustained work of about ten people. Among recipients of the Righteous Among the Nations medal, awarded by the State of Israel to non-Jews who saved Jews from the Holocaust, Polish citizens form the largest national group. To date, 6,339 Polish men and women have been recognized as Righteous. That is more than a quarter of the 22,765 honorary titles awarded worldwide, a scale of individual risk that ran alongside a very different kind of resistance building elsewhere in occupied Poland.

• 4. The Underground Army

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  The Armia Krajowa, or Home Army, numbered some 400,000 fighters at its peak, making it one of the three largest resistance movements of the war. Coordinated with the exiled Polish government in London, its operations centered on sabotage, diversion and intelligence gathering. Combat activity stayed low through most of the war, since the Home Army was avoiding suicidal fighting and preserving its limited resources. Even so, its units carried out thousands of raids and intelligence operations, bombed hundreds of railway shipments, and carried out tens of thousands of acts of industrial sabotage before its major uprising. Some operations targeted Gestapo officials directly, assassinating those responsible for Nazi terror.

  After Germany attacked the Soviet Union in 1941, the Home Army sabotaged the German advance into Soviet territory and fed intelligence on German troop movements. Its direct combat activity increased sharply after 1943, as the Nazi war machine began to crumble under Red Army pressure. That shift culminated in a nationwide uprising codenamed Operation Tempest. German losses to Polish partisans climbed to an average of 850-1,700 per month in early 1944, up from about 250-320 per month back in 1942.

  Alongside the Home Army stood the Narodowe Siły Zbrojne, or National Armed Forces, an underground ultra-nationalist group fiercely opposed to communism. It fought German units and won many skirmishes, while from 1943 some of its units also battled the communist Gwardia Ludowa and Polish People's Army PAL. By 1944, the advancing Red Army looked to these fighters like another foreign occupier, sparking skirmishes with Soviet troops and Soviet-backed partisans as well. The Armia Ludowa, a separate Soviet-aligned force unconnected to the government in London, had absorbed the Gwardia Ludowa and PAL by July 1944 and numbered about 6,000 soldiers, though estimates vary.

  Polish Jews organized their own resistance too, split between the right-wing Żydowski Związek Walki, or Jewish Fighting Union, and the more Soviet-leaning Żydowska Organizacja Bojowa, or Jewish Combat Organization. The two groups cooperated with each other only rarely. Their ties to the wider Polish resistance ranged from occasional cooperation, mostly between the Jewish Fighting Union and the Home Army, to open armed confrontation, mostly involving the Jewish Combat Organization and the National Armed Forces. A further resistance body, the mostly peasant Bataliony Chłopskie, was allied to the Home Army and grew to 115,543 members by 1944, with an unconfirmed estimated total near 150,250 once affiliated units are counted. That patchwork of armies, each guarding its own loyalties, still depended on a single hidden asset: intelligence smuggled out of occupied Poland to London and beyond.

• 5. Breaking Enigma

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  Marian Rejewski, Henryk Zygalski and Jerzy Różycki, three mathematician-cryptologists at the Polish General Staff's Cipher Bureau in Warsaw, spent more than six and a half years, from late December 1932 until the outbreak of the war, developing ways to break the German Enigma cipher machine. Their toolkit included the grill method, Różycki's clock, Rejewski's cyclometer and card catalog, Zygalski's perforated sheets, and Rejewski's cryptologic bomba, the direct ancestor of the later British Bombe. On the 25th of July 1939, just five weeks before the war began, Poland shared these results with France and the United Kingdom at Pyry in the Kabaty Woods south of Warsaw. Neither country had managed to crack the German military Enigma cipher on its own. Had Poland not shared its results at Pyry, Britain might never have been able to read Enigma traffic at all. Intelligence from that source, codenamed Ultra, proved extremely valuable to the Allied war effort, even though historians still debate its precise influence.

  From 1940, Polish agents including Witold Pilecki got inside German concentration camps such as Auschwitz and reported Nazi atrocities to the outside world. Jan Karski, another Polish resistance figure, briefed the government-in-exile and the Western Allies on conditions in occupied Poland, including the destruction of the Warsaw Ghetto and the existence of secret extermination camps. Home Army intelligence later proved vital to locating and, on the 18th of August 1943, helping destroy the German rocket facility at Peenemünde, along with gathering information on the V-1 flying bomb and V-2 rocket. After a V-2 test rocket fired on the 30th of May 1944 crashed near a German facility at Sarnaki on the Bug River, the Home Army recovered it, and on the night of the 25th to the 26th of July 1944 flew its crucial parts to Britain aboard an RAF plane, together with drawings of parts too large to carry.

  The II Bureau, the exiled Polish government's intelligence service, reached well beyond Poland and even beyond Europe. It reported on German war production, morale, troop movements and submarine operations, and reportedly ran two agents inside the upper levels of the German high command. In July 1941, Mieczysław Słowikowski, known by the codename Rygor, set up Agency Africa, one of the most successful intelligence operations of the entire war, with help from Lt. Col. Gwido Langer and Major Maksymilian Ciężki, prewar heads of Poland's Cipher Bureau and its Enigma-breaking section. Its reports fed directly into American and British planning for the Operation Torch landings in North Africa in November 1942, the first large-scale Allied landings of the war. Krystyna Skarbek, known abroad as Christine Granville, served in Britain's Special Operations Executive, one of several Poles who worked inside other Allied intelligence services.

  Across the war, 48 percent of all reports the British secret services received from continental Europe came from Polish sources, out of roughly 80,000 reports in total, 85 percent of them judged high quality or better. The Polish network kept growing even under occupation, reaching more than 1,600 registered agents by one estimate, or as many as 3,500 by another. A 2005 report from the Anglo-Polish Historical Committee called that contribution disproportionately large, and its authors argued that Home Army intelligence supported the Allied war effort far more effectively than the fighting carried out by resistance and guerrilla units. That verdict on intelligence sat alongside a different story unfolding on foreign battlefields, where Polish soldiers, airmen and sailors were rebuilding conventional armed forces almost from scratch.

• 6. Wings Over Britain

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  The Polish Air Force first went into action during the 1939 invasion, badly outnumbered and flying fighters already outclassed by newer German designs. It stayed active into the campaign's second week and still managed to damage the Luftwaffe significantly. The Luftwaffe lost 285 aircraft to all causes with 279 more damaged, while Polish losses ran to 333 aircraft. Many Polish pilots then escaped through Hungary to France, where they flew as fighter squadron GC 1/145 and in smaller detached units, along with industrial-defense flights, a total of 133 pilots who claimed 53-57 victories for the loss of 8 men, about 7.93 percent of all Allied victories in that campaign.

  On the 11th of June 1940, the Polish Government-in-Exile signed an agreement with the British Government to form a Polish Army and Polish Air Force in the United Kingdom. The first two of an eventual ten Polish fighter squadrons went into action that August. Four Polish squadrons fought in the Battle of Britain, the 300 and 301 Bomber Squadrons and the 302 and 303 Fighter Squadrons, with 89 Polish pilots between them. Counting more than 50 additional Poles flying in British squadrons, 145 Polish pilots defended British skies in total. Most of them were already combat veterans of the 1939 campaign in Poland and the 1940 Battle of France, and prewar Poland had set an unusually high standard of pilot training.

  No. 303 Squadron, named for the Polish-American general Tadeusz Kościuszko, claimed 126 kills, the highest total of any fighter squadron in the Battle of Britain, despite only entering combat on the 30th of August 1940. Making up just 5 percent of the pilots active in the battle, Polish airmen were responsible for 12 percent of all victories. In 1943 Polish pilots fought again in Tunisia as the Polish Fighting Team, nicknamed Skalski's Circus, and flew bombing raids over Germany from 1940 to 1945. Through the second half of 1941 and early 1942, Polish bomber squadrons made up a sixth of RAF Bomber Command's strength before suffering heavy losses with little replenishment. Between 1940 and 1945, 929 Polish aircrew serving with Bomber Command were killed.

  By May 1945, eight Polish fighter squadrons flying within the RAF had been credited with 629 Axis aircraft destroyed, part of a wartime tally, recorded with fractional credit for shared kills, of 769 aircraft destroyed, 177 probable and 252 damaged. By the war's end, about 19,400 Poles were serving in the Royal Air Force. That figure sat inside a far larger reconstruction effort, one that also rebuilt Polish armies and a Polish navy from almost nothing after 1939.

• 7. Soldiers of Many Uniforms

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  After Poland's defeat in the 1939 campaign, the government-in-exile organized a new army of about 75,000 men in France. In 1940 the Polish Highland Brigade fought at the Battle of Narvik in Norway, while two Polish divisions, the 1st Grenadier Division and the 2nd Infantry Fusiliers Division, took part in the defense of France, alongside a forming motorized brigade and two more infantry divisions. A Polish Independent Carpathian Brigade formed in French Mandate Syria from troops who had escaped through Romania, while the Polish Air Force in France flew 86 aircraft, one and a half squadrons fully operational and the rest still training.

  By the fall of France, many Polish personnel had died in the fighting or been interned in Switzerland, but about 19,000 Poles, roughly a quarter of them aircrew, were evacuated to the United Kingdom. In 1941, following an agreement between the government-in-exile and Joseph Stalin, the Soviets released Polish citizens to form a 75,000-strong army under General Władysław Anders. With no Soviet support to train or equip it, Anders had the force transferred across the Caspian Sea to Iran in March and August 1942, freeing Soviet divisions stationed there for other duties. In the Middle East, Anders' Army joined the British Eighth Army as the Polish II Corps.

  The Polish Armed Forces in the West, fighting under British command, numbered 195,000 in March 1944 and 165,000 by the end of that year, including about 20,000 airmen and 3,000 sailors. By July 1945, after recruitment was halted, the force had grown to 228,000, most of the newcomers freed prisoners of war and former labor-camp inmates. Roughly 26,830 of its soldiers had by then been killed, gone missing, or died of wounds.

  On the eve of the war, three Polish destroyers had already been sent to the safety of the United Kingdom under Operation Peking, and went on to fight alongside the Royal Navy. Britain supplied further ships and submarines that its own crews could not staff, and across the war the Polish Navy operated 27 vessels in total: 2 cruisers, 9 destroyers, 5 submarines and 11 torpedo boats. Those crews sailed 1.2 million nautical miles, escorted 787 convoys and ran 1,162 patrols and combat operations, sinking 12 enemy ships, including 5 submarines, and 41 merchant vessels, while damaging 24 more and shooting down 20 aircraft. Of more than 4,000 sailors who served, 450 were killed in action, and the Polish Merchant Navy separately lost 18 ships and over 200 sailors while carrying Allied cargo.

  In the Soviet Union, the Union of Polish Patriots, a communist organization founded in 1943, built a new army from ethnic Poles who had remained on Soviet soil, many of them deported after the Soviet annexation of eastern Poland. That division, nicknamed the Berling Army after commander Zygmunt Berling, made its combat debut at the Battle of Lenino in October 1943 before growing into the 1st Polish Corps and then the 1st Polish Army; a 2nd Polish Army followed in 1945. The Polish First Army entered Poland from Soviet territory in 1944 as part of the 1st Belorussian Front, liberated the Warsaw suburb of Praga during the Warsaw Uprising, fought at Bydgoszcz, Kolobrzeg, Gdańsk and Gdynia, and joined the final capture of Berlin in April and May 1945, losing about 17,500 soldiers killed over the war. The Polish Second Army fought with the Soviet 1st Ukrainian Front in the Prague Offensive; together the two armies of this Polish People's Army suffered about 67,000 casualties in the war's final operations.

  Germany conscripted several hundred thousand former Polish citizens, particularly people living in territory it had annexed, into its armed forces, while some members of Poland's prewar German minority volunteered and, in 1939, formed the paramilitary Volksdeutscher Selbstschutz to support German occupation forces. Nearly 90,000 of these German military personnel, captured as prisoners of war on the Western Front, were later recruited into the Polish Armed Forces in the West. By Victory Day on the 9th of May 1945, a third of Polish service members there had once worn German uniforms. That single statistic hints at how thoroughly the war had scrambled Polish identity, even as Polish engineers kept inventing tools purpose-built to fight it.

• 8. Ingenuity Under Occupation

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  Józef Kosacki invented the Polish mine detector, put to use by the Allies from 1942 onward. Engineer Rudolf Gundlach had already patented another Polish design in 1936, the Gundlach Peryskop obrotowy, a rotating tank periscope first fitted to Polish 7TP and TKS tanks. Sold to the British for a nominal sum, it let a tank commander see backward without turning his head, and it went on to equip most tanks of the war, including the Soviet T-34, the British Crusader, Churchill, Valentine and Cromwell, and the American M4 Sherman. German forces later adopted the design extensively as well.

  Adopted in 1935 as the Polish Army's standard sidearm, the pistolet wz. 35 Vis, often called the Radom in English, was a 9 millimeter single-action semi-automatic pistol. Germany appropriated the design, and between 1939 and 1945 produced some 312,000-380,000 of them for its paratroopers and police as the Pistole 35(p). The PZL.37 Łoś, a twin-engine medium bomber designed in the mid-1930s by Jerzy Dąbrowski at the PZL factory in Warsaw, flew operationally in the 1939 invasion, and its laminar-flow wing made it one of the most advanced bombers in the world before the war.

  Władysław Świątecki patented a bomb-release system, the Świątecki bomb slip, in Poland and abroad in 1926, after inventing it the year before. Components of it went into the prewar PZL.37 Łoś. The British adopted it in 1940 for the Avro Lancaster bomber, and in 1943 Jerzy Rudlicki updated the design for the American B-17 Flying Fortress. Józef Maroszek secretly developed the Wz. 35 anti-tank rifle, a 7.92 millimeter weapon built from the Mauser rifle with its own high-velocity cartridge, capable of over 1,000 meters per second and effective at 100 meters against every German tank of the period, including the Panzer I, II and III as well as Czech-made LT-35 and LT-38 tanks in German service.

  Solving the technical problem of tracking German Kriegsmarine radio transmissions from moving ships, Polish engineer Waclaw Struszynski led the team that built the first practical high-frequency direction-finding system at England's Admiralty Signal Establishment. Installed on convoy escort ships, it proved highly effective against U-boats in the Battle of the Atlantic. His father, Professor Marceli Struszyński, a member of the Polish resistance, separately analyzed the fuel used in the German V-2 rocket and sent the formula to England. Henryk Magnuski, a Polish engineer working for Motorola, co-designed the SCR-300 radio in 1940, the first small radio transceiver with manually set frequencies, later used widely by the American Army under the nickname walkie-talkie.

  Beyond individual inventions, a Polish, Czech and British team turned the 20 millimeter Polsten cannon into a simpler, cheaper version of the Oerlikon 20 millimeter gun. The Home Army was likely the only World War II resistance movement to manufacture weapons and munitions on a large scale, producing the Błyskawica submachine gun along with the Bechowiec, KIS and Polski Sten machine pistols, the last adapted from the British Sten, plus filipinka and sidolówka hand grenades. During the Warsaw Uprising its engineers even built armored cars such as the Kubuś. The KIS itself was designed and built inside Jan Piwnik's guerrilla unit, nicknamed Ponury or Grim, operating in the Holy Cross Mountains, likely the only modern firearm of the entire war built in a forest without factory tools or equipment.