From the very beginning of war against Poland, German forces carried out massacres and executions of civilians.
Many of these atrocities were not properly researched after the war due to the political divide between Eastern and Western Europe during the Cold War, wrote Böhler.
Polish eyewitness accounts do not identify the German units involved; that information is traceable only through German records.
Therefore, the crimes committed by the Heer (the regular German army) were often wrongly attributed to SS operational groups in Polish historiography.
It is estimated that there were two hundred executions every day in September 1939.
Reinhard Heydrich, head of the Reich Main Security Office, complained that the rate was too slow.
Typically, the mass executions were conducted in public spaces such as the town square in order to inflict terror.

Records show that during the German advance across Poland five hundred thirty-one towns and villages were burned.
By the end of September 1939 the names of settlements, dates and numbers of civilians executed by the Wehrmacht included: Starogard (2 September), 190 Poles, 40 of them Jews; Świekatowo (3 September), 26 Poles; Wieruszów (3 September), 20 Poles all Jews.
On 4 September 1939 the 42nd Infantry Regiment committed the Częstochowa massacre with 1,140 citizens or more, 150 of them Jews, murdered in wild shooting actions in several city locations, leading to a final bloodbath according to Polish reports, involving frightened and inexperienced troops opening machine gun fire at a crowd of 10,000 civilians rounded up as hostages in the Main Square.
The official Wehrmacht tally listed only 96 male and 3 female victims of the so-called "anti-partisan" action in the city.

In Imielin (4–5 September), 28 Poles were killed; in Kajetanowice (5 September), 72 civilians were massacred in revenge for two German horses killed by German friendly fire; Trzebinia (5 September), 97 Polish citizens; Piotrków (5 September), Jewish section of the city was set on fire; Będzin (8 September), two hundred civilians burned to death; Kłecko (9–10 September), three hundred citizens executed; Mszadla (10 September), 153 Poles; Gmina Besko (11 September), 21 Poles; Kowalewice (11 September), 23 Poles; Pilica (12 September); 36 Poles, 32 of them Jewish; Olszewo (13 September), 13 people (half of the village) from Olszewo and 10 from nearby Pietkowo including women and children stabbed by bayonets, shot, blown up by grenades, and burned alive in a barn; Mielec (13 September), 55 Jews burned to death; Piątek (13 September), 50 Poles, seven of them Jews.
On 14–15 September about 900 Polish Jews, mostly intelligentsia, were targeted in parallel shooting actions in Przemyśl and in Medyka; this was a foreshadowing of the Holocaust to come.
Roughly at the same time, in Solec (14 September), 44 Poles killed; soon thereafter in Chojnice, 40 Polish citizens; Gmina Kłecko, 23 Poles; Bądków, 22 Poles; Dynów, two hundred Polish Jews.
Public executions continued well beyond September, including in municipalities such as Wieruszów County, Gmina Besko, Gmina Gidle, Gmina Kłecko, Gmina Ryczywół, and Gmina Siennica, among others.

In the town of Bydgoszcz, the Volksdeutscher Selbstschutz (German Fifth Column) attempted to aid the invading German forces by shooting at the Polish Army.
A number of saboteurs were executed by the Poles for treason, including for possession of military weapons.
The Nazi German government in its own communiqués dubbed the Bydgoszcz incident Bloody Sunday, and claimed the wholesale slaughter of Germans in the city, which was not true.
When Bydgoszcz was taken over by the Wehrmacht in October, designated killing squads began murdering civilian Poles in revenge at the Valley of Death (Bydgoszcz); some 20,000 died in all.

Along with civilians, captured Polish Army soldiers were also massacred.
On the very first day of invasion (1 September 1939), Polish prisoners of war (POWs) were murdered by the Wehrmacht at Pilchowice, Czuchów, Gierałtowice, Bojków, Lubliniec, Kochcice, Zawiść, Ornontowice and Wyry.
From the very beginning of war against Poland, German forces carried out massacres and executions of civilians. Many of these atrocities were not properly researched after the war due to the political divide between Eastern and Western Europe during the Cold War, wrote Böhler. Polish eyewitness accounts do not identify the German units involved; that information is traceable only through German records. Therefore, the crimes committed by the Heer (the regular German army) were often wrongly attributed to SS operational groups in Polish historiography. It is estimated that there were two hundred executions every day in September 1939. Reinhard Heydrich, head of the Reich Main Security Office, complained that the rate was too slow. Typically, the mass executions were conducted in public spaces such as the town square in order to inflict terror.
Records show that during the German advance across Poland five hundred thirty-one towns and villages were burned. By the end of September 1939 the names of settlements, dates and numbers of civilians executed by the Wehrmacht included: Starogard (2 September), 190 Poles, 40 of them Jews; Świekatowo (3 September), 26 Poles; Wieruszów (3 September), 20 Poles all Jews. On 4 September 1939 the 42nd Infantry Regiment committed the Częstochowa massacre with 1,140 citizens or more, 150 of them Jews, murdered in wild shooting actions in several city locations, leading to a final bloodbath according to Polish reports, involving frightened and inexperienced troops opening machine gun fire at a crowd of 10,000 civilians rounded up as hostages in the Main Square. The official Wehrmacht tally listed only 96 male and 3 female victims of the so-called "anti-partisan" action in the city.
In Imielin (4–5 September), 28 Poles were killed; in Kajetanowice (5 September), 72 civilians were massacred in revenge for two German horses killed by German friendly fire; Trzebinia (5 September), 97 Polish citizens; Piotrków (5 September), Jewish section of the city was set on fire; Będzin (8 September), two hundred civilians burned to death; Kłecko (9–10 September), three hundred citizens executed; Mszadla (10 September), 153 Poles; Gmina Besko (11 September), 21 Poles; Kowalewice (11 September), 23 Poles; Pilica (12 September); 36 Poles, 32 of them Jewish; Olszewo (13 September), 13 people (half of the village) from Olszewo and 10 from nearby Pietkowo including women and children stabbed by bayonets, shot, blown up by grenades, and burned alive in a barn; Mielec (13 September), 55 Jews burned to death; Piątek (13 September), 50 Poles, seven of them Jews. On 14–15 September about 900 Polish Jews, mostly intelligentsia, were targeted in parallel shooting actions in Przemyśl and in Medyka; this was a foreshadowing of the Holocaust to come. Roughly at the same time, in Solec (14 September), 44 Poles killed; soon thereafter in Chojnice, 40 Polish citizens; Gmina Kłecko, 23 Poles; Bądków, 22 Poles; Dynów, two hundred Polish Jews. Public executions continued well beyond September, including in municipalities such as Wieruszów County, Gmina Besko, Gmina Gidle, Gmina Kłecko, Gmina Ryczywół, and Gmina Siennica, among others.
In the town of Bydgoszcz, the Volksdeutscher Selbstschutz (German Fifth Column) attempted to aid the invading German forces by shooting at the Polish Army. A number of saboteurs were executed by the Poles for treason, including for possession of military weapons. The Nazi German government in its own communiqués dubbed the Bydgoszcz incident Bloody Sunday, and claimed the wholesale slaughter of Germans in the city, which was not true. When Bydgoszcz was taken over by the Wehrmacht in October, designated killing squads began murdering civilian Poles in revenge at the Valley of Death (Bydgoszcz); some 20,000 died in all.
Along with civilians, captured Polish Army soldiers were also massacred. On the very first day of invasion (1 September 1939), Polish prisoners of war (POWs) were murdered by the Wehrmacht at Pilchowice, Czuchów, Gierałtowice, Bojków, Lubliniec, Kochcice, Zawiść, Ornontowice and Wyry.
War crimes in occupied Poland during World War II