During the German invasion of Poland, which started World War II, Nazi Germany carried out a number of atrocities involving Polish prisoners of war (POWs). During that period, the Wehrmacht is estimated to have mass-murdered at least 3,000 Polish POWs, with the largest atrocities being the Ciepielów massacre of 8 September 1939 (~300 victims) and the Zambrów massacre of 13–14 September (~200 victims). Most of those atrocities are classified as war crimes of the Wehrmacht. Jewish soldiers with the Polish Army were also more likely than others to be victims of various atrocities.

A number of other atrocities against Polish POWs occurred later in the war, particularly on the Eastern Front, with the largest atrocities in 1945 committed at Podgaje (~200 victims) and Horka (~300 victims).

Background

Before the war began, the Wehrmacht high command issued many radical and racist communiqués to its soldiers. In them, it warned soldiers against the alleged "fanatic" hatred of Poles towards the Germans and warned them to expect guerrilla warfare, sabotage and diversion, likely to be organized by Polish soldiers dressed in civilian clothes. This mentality likely increased the number of atrocities committed by the Germans on both Polish prisoners of war and civilians. According to Geoffrey P. Megargee, such war crimes were the result of contempt for Poles and Polish soldiers, encouraged by Nazi propaganda, which described them as German-hating Untermenschen; and lack of preparation, resources, and will to secure surrendered Polish soldiers. In addition, plans formulated by the German General Staff, prior to the invasion, authorized the SS to carry out security tasks on behalf of the army that included the imprisonment or execution of Polish citizens, whether Jewish or gentile.

Further, German officers often treated Polish soldiers of disorganized units captured behind German lines as partisans, not as regular soldiers, and felt justified in ordering their summary executions. On 4 September 1939, the Einsatzgruppen operating in Poland received an instruction to immediately court-martial and execute all alleged Polish partisans (Freischärler). In fact, this instruction led to mass executions of members belonging to Polish paramilitary formations and ad-hoc citizens watches (Straże Obywatelskie). These individuals were routinely labeled as "partisans" and summarily executed, even though they openly carried weapons and wore identifying marks or armbands as required by the Hague Convention.

Invasion of Poland

Numerous examples exist in which Polish soldiers were killed after capture. Polish historian Szymon Datner listed 64 "instances of Polish prisoners being shot in captivity", and a number of other executions "where there had been some supposed provocation". Timothy Snyder, an American historian wrote that over 3,000 Polish POWs were killed in at least 63 separate shooting actions in which they were often forced to take their uniforms off. German historian Jochen Böhler also provided the same estimate, writing that the Wehrmacht mass murdered at least 3,000 Polish POWs during the campaign. Polish-American historian Tadeusz Piotrowski estimated the victims to be 1,000 POWs executed by the German army in September 1939, several hundred more executed by Gestapo, and about 1,200 members of the National Defense, as well as other volunteers like the post office workers involved in the Defence of the Polish Post Office in Danzig. Bob Moore suggested an even higher estimate, writing that "some 10,000 Polish servicemen who should have been considered as prisoners of war died at the hands of their captors during and immediately after the five weeks of war."

Already on the first day of invasion (1 September 1939), Polish POWs were murdered by the Wehrmacht at: Pilchowice, Czuchów, Gierałtowice, Bojków, Lubliniec, Kochcice, Zawiść, Ornontowice and Wyry.

Polish historian Tomasz Sudoł notes that several dozen of larger incidents can be documented, and that the number of smaller incidents – such as executions of individual soldiers – is "significant", but hard to estimate. With regards to the larger incidents, he mentions, chronologically, the massacres at:

Bydgoszcz, where over 40 members of the local Citizens Watch, despite being guaranteed security by the Wehrmacht upon the capitulation, were handed over to the Einsatzgruppen and executed on 5 September. Some of them were beaten to death. Serock, where over 80 Polish prisoners of war were killed by the German troops (the Serock massacre of 5 September 1939); , where 19 Polish officers, prisoners of war, were executed on 6 September; several additional soldiers were executed around the same time in the nearby village of Longinówka; Mszczonów, where 11 Polish prisoners were executed by the 4th Panzer Division on 8 September; Piaseczno, where 21 Polish prisoners were executed, also on 8 September; Ciepielów, where about 300 POWs were killed (the Ciepielów massacre of 8 September 1939, carried out by the 29th Motorized Infantry Division); Stare Kozłowice, where 5 POWs were executed by the 2nd Light Division on 12 September; Szczucin, where about 40 POWs and 30 civilians were killed, also on 12 September (the Szczucin massacre); Zambrów, where a further 200 POWs were killed (the Zambrów massacre on the night of 13–14 September 1939); Śladów, where 252 POWs, or according to other sources – about 150 POWs and 150 civilians, were shot or drowned, probably by the 4th Panzer Division (the Śladów massacre of 18 September); Majdan Wielki, where 42 POWs were killed (the Majdan Wielki massacre of 20 September) Urych (formerly Urycz), where about 70–100 POWs were herded into a barn and burned alive (the Urycz massacre of 22 September) Sochaczew's district of , where 50 POWs were killed (the Boryszew massacre of 22 September, sometimes called the Sochaczew massacre), and Zakroczym, where several hundred POWs were killed (the Zakroczym massacre of 28 September).

There were also incidents such as the Katowice massacre on 4 September, where among the 80 or so victims of local militia, it is estimated that there were some Polish soldiers who failed to evacuate with the larger formations.

In addition to massacres of POWs, there have been instances of refusal to provide medical aid to wounded soldiers, torture and other abuse of prisoners and repression against families and other relatives of the soldiers.

The prisoners in the temporary POW camp in Żyrardów, captured after the Battle of the Bzura, were denied any food and starved for ten days. In some cases Polish POWs were burned alive. Units of the Polish 7th Infantry Division were massacred after being captured in several individual acts of revenge for their resistance in combat. On 11 September, Wehrmacht soldiers threw hand grenades into a school building where they kept Polish POWs. In one documented incident, German tanks shelled a clearly marked Polish field hospital. On 14 September 1939, troops of the 206th Infantry Division perpetrated a massacre of 30 Polish POWs and 23 civilians in Olszewo, in revenge for the losses suffered in the battle against the Suwalska Cavalry Brigade.

Most of those atrocities are classified as war crimes of the Wehrmacht, as they occurred during the period of military occupation of Poland (untll 25 September).

German atrocities against Polish POWs have been discussed in the context of German later and even more extreme atrocities against Soviet POWs, as setting the stage for them. They have also led a number of historians to conclude that Germany violated the Geneva convection from early days of the war.

Fate of Jewish POWs

As a prelude to The Holocaust, Polish POWs of Jewish origin were routinely selected and shot on the spot.

In transit camps for the Polish prisoners of war (, Durchgangslagers or Dulags) as well as in Stalags where privates and non-commissioned officers were held, the German military authorities established "inner ghettos" where Jewish POWs, were segregated from non-Jewish soldiers of the Polish Armed Forces. The treatment of Jewish POWs was harsher, and they were often assigned the most strenuous and degrading labor tasks. The Germans had plans to establish "inner ghettos" in Oflags as well, but in many cases they encountered opposition from Polish officers. Ultimately, for reasons unknown, "inner ghettos" for Jewish officers were only created in certain Oflags.

In December 1939 the German military authorities initiated the process of releasing the Jewish privates and NCOs from Stalags. In most cases, these soldiers were transferred to the labor camp at Lipowa Street in Lublin, which at that time also served as a transit camp for Jewish POWs. Due to the harsh conditions during transportation, many of them perished from freezing temperatures or died of starvation in the freight cars. The fate of approximately 500 Jewish POWs, who before the war had resided in Polish territories now annexed by Nazi Germany, was particularly tragic. In February 1940, as the Judenrat in Lublin refused to accommodate them, the Germans forced the POWs to undertake a march on foot, enduring freezing temperatures, to the city of Biała Podlaska, located 130 kilometers away. During this "death march", several hundred POWs were murdered. The remaining POWs were transferred from Lipowa Street camp to ghettos in the General Government before the end of May 1940. When Operation Reinhard commenced, they shared the same fate as other Jews.

Between December 1940 and February 1941, a minimum of 2,120 Jewish POWs, who had previously lived in Polish territories that were annexed by the Soviet Union, were permanently imprisoned at the Lipowa Street camp. The majority of them were murdered during the operation Harvest Festival in November 1943.

The fate of the Jewish officers was different. They remained in Oflags and majority of them survived the war.

Conditions in POW camps

Polish POWs were held in German camps (Oflags for officers and Stalags for soldiers of lower ranks). Polish POWs at POW camps, temporary or long-term, have been poorly treated; Bob Moore noted that "some of the [poor] conditions could be ascribed to the speed of the German victory and the lack of adequate preparation, [but] there is no doubt that ill-treatment was also deliberately inflicted." Conditions of Polish POWs have been described as "much worse" than those of Western Allies with numerous infractions of the conditions stipulated by the Geneva convection. Some prisoners died due to malnutrition and environmental conditions; for example in January 1940 a group of 2,000 sick POWs were decreed to be released and transported from Germany to Poland; however, a tenth of them have frozen to death during the transport. Some POWs were used as forced laborers. Within several months, almost all non-officer prisoners of war (estimates range at 300,000-480,000) were stripped of their POW status and forced to work in Nazi Germany. Few dozens Polish officers were executed after having been recaptured during the failed escape attempt in 1943 from the Oflag VI-B.

Treatment of deserters

Germany conscripted some Poles into its army; subsequently, some switched sides and joined the Allies side. Germans treated those who have been captured not as POWs but as deserters, to be put on trial.

Warsaw Uprising