Bloody Sunday ( 1939 ) Bloody Sunday ( ; ) was a series of killings against the German minority that took place at the beginning of World War II . On September 3 , 1939 , two days after the beginning of the German invasion of Poland , highly controversial killings occurred in and around Bydgoszcz ( ) , a Polish city with a sizable German minority . The number of casualties and other details of the incident are disputed among historians . The Nazis exploited the deaths as grounds for a massacre of Polish inhabitants after the Wehrmacht captured the town . Terminology . The term " Bloody sunday " was created and supported by the Nazi - propaganda officials . An instruction issued by the Ministry of Propaganda for the press said : Background . Bydgoszcz ( Bromberg ) was part of the Polish - Lithuanian Commonwealth until 1772 , when it was annexed by the Kingdom of Prussia during the First Partition of Poland . As a part of Prussia , the city was affected by the unification of Germany in 1871 and became part of the German Empire . It would remain a part of the German Empire until the end of World War I . In February 1920 , the Treaty of Versailles awarded the city and the surrounding region to the Second Polish Republic ( the administrative region of Pomeranian Voivodeship ) . This resulted in a number of ethnic Germans leaving the region for Germany . Over the interwar period , the German population decreased even further . The 1931 Polish Census reported the German population in the city was 117 , 200 ; according to the German historian Hugo Rasmus , only about 10 , 000 Germans remained by 1939 . The emergence of the Nazi Party in Germany had an important impact on the city . Adolf Hitler revitalized the Völkisch movement , making an appeal to the Germans living outside of Germany ' s post - World War I borders . It was Hitler ' s explicit goal to reverse the work of the Treaty of Versailles and create a Greater German State . By March 1939 , these ambitions , charges of atrocities on both sides of the German - Polish border , distrust , and rising nationalist sentiment led to the complete deterioration of Polish - German relations . Hitler ' s demands for the Polish Corridor and , Polish opposition to negotiations with him fueled ethnic tensions . For months prior to the 1939 German invasion of Poland , invasion , German newspapers and politicians like Adolf Hitler had carried out a national and international propaganda campaign accusing Polish authorities of organizing or tolerating violent ethnic cleansing of ethnic German s living in Poland . After armed conflict erupted on September 1 , 1939 , statements that persecutions of ethnic Germans had occurred in Poland , especially in Bydgoszcz , continued to appear in the Nazi press . It was a part of campaign accusing Polish authorities of organising or tolerating violent ethnic cleansing of Germans living in Poland . Bloody Sunday . According to the most widely accepted version , the incident stemmed from groups of German saboteurs attacking Polish troops behind the front line s . This version holds that , as a contingent of the Polish Army was withdrawing through Bydgoszcz ( Army Pomorze ' s 9th , 15th , and 27th Infantry Division ) it was attacked by German irregular s from within the city . According to a British witness , a retreating Polish artillery unit was shot at by Germans from within a house ; the Poles returned fire and were subsequently shot at from a Jesuit church . In the ensuing fight both sides suffered some casualties ; captured German nonuniformed armed insurgents were executed on the spot and some mob lynching was also reported . A Polish investigation concluded in 2004 that Polish troops had been shot at by members of the German minority and German military intelligence ( Abwehr ) agents ; around 40 – 50 Poles and between 100 to 300 Germans were killed . The Wehrmacht War Crimes Bureau investigation in 1939 – 1940 concluded that the events were a result of panic and confusion among the Polish troops . The Wehrmacht investigation included the interrogation of captive Polish soldiers , ethnic Germans from Bydgoszcz and surrounding villages , and Polish civilians . The bodies of the victims were exhumed and the cause of death and the possible involvement of military rifles was assessed . According to this investigation , a squad of Polish soldiers was sent in to clarify the situation after hearing shots being fired within the city . Uniformed Polish soldiers , assisted by the local Polish population , were led to houses from which shots were allegedly heard . In households where weapons were found , people were subject to summary executions . German reprisals and further atrocities . The killings were followed by German reprisals and oppression , including a " de - Polonisation " campaign . In an act of retaliation for the killings on Bloody Sunday , a number of Polish civilians were executed by German military units of the Einsatzgruppen , Waffen SS , and Wehrmacht . According to German historian Christian Raitz von Frentz , 876 Poles were tried by German tribunal for involvement in the events of Bloody Sunday before the end of 1939 . 87 men and 13 women were sentenced without the right to appeal . Polish historian Czesław Madajczyk notes 120 executions in relation to Bloody Sunday , and the execution of 20 hostages after a German soldier was allegedly attacked by a Polish sniper . According to a German version , Polish snipers attacked German troops in Bydgoszcz for several days ( Polish sources and witnesses do not confirm this ) . The German governor , General Walter Braemer , ( the commander of the rear army area ) , ordered the execution of 80 Polish hostages over the next few days . By September 8 , between 200 to 400 Polish civilians had been killed . According to Richard Rhodes , a number of Boy Scouts were set up in the marketplace against a wall and shot ; a devoted priest who rushed to administer the last sacrament was shot too , receiving five wounds . Murders continued all week ; 34 of the leading tradespeople and merchants of the town were shot , as well as many other leading citizens . Many Poles , particularly members of the intelligentsia and the Jews , were singled out for deportation , or killed outright . More than 20 , 000 Polish citizens of Bydgoszcz ( 14 % of the population ) were either shot or died in concentration camps during the occupation . The debate in scholarship . The exact number of victims of Bloody Sunday is disputed . Peter Aurich ( a pseudonym of the German journalist Peter Nasarski ) put the number of German civilian deaths in Bydgoszcz at 366 , while Hugo Rasmus estimates it as at least 415 . Two Polish historians , Włodzimierz Jastrzębski and Czesław Madajczyk , estimate ethnic German deaths at 103 ( Jastrzębski ) , and about 300 ( 150 on September 3 , the rest in the days after ) . The Polish historians point out that since these losses occurred during actual combat , most of the civilian losses should be attributed to accidents common in urban combat conditions ; they argue that civilian losses might have occurred when the town was attacked by the German airforce ( Luftwaffe ) . Strafing civilians in the town by the Luftwaffe is confirmed by German witnesses . Nazi propaganda reinforced Polish perceptions of the German minority as hostile , and during the invasion reported that the German minority was aiding the forces . This contributed Polish misconceptions , as the Poles were expecting the German minority to be actively hostile . An even bigger debate in the scholarship concerns the question whether — as the Polish historiography suggests — there were indeed any members of a German fifth column in the city who opened fire on the Polish troops ( and if so , whether they were composed of members of the Bydgoszcz German minority or not ) , or whether — as critics among the German historiography argue — Polish troops ( or panicking civilians ) overreacted in the confusion and targeted innocent German civilians . The account of Peter Nasarski alias Aurich has been called by Harry Gordon one of the most thorough German accounts ; his work is however generally rejected in Poland , perhaps because he indiscriminately used witness statements collected by Nazi officials . According to Nasarski , after police forces retreated from Bydgoszcz , agitated Polish civilians accused many Germans of assaulting Polish soldiers and executed them and any Poles who stood up in their defence . Rasmus attributes the situation to confusion and the disorganised state of the Polish forces in the city . von Frentz wrote that " In Bydgoszcz , the event was probably caused by confusion among the rapidly retreating soldiers , a general breakdown in public order and panic among the Polish majority after two German air raids and the discovery of a small reconnaissance group of the German Army on the previous day . " He quotes Nazi German reports about the civilian victims and atrocities , later corroborated by a Red Cross commission that the Nazis invited to the scene . von Frentz also noted that eyewitness accounts of atrocities committed against the German population are as unreliable as Polish accounts of the fifth columnists . No ethnic Germans are known to have spoken of participation in that event . In the post - war collaboration trials , no ethnic German was charged in relation to Bloody Sunday . Another counterargument to the fifth column theory is that Polish troops were being targeted by advance units of the German regular army ( Heer ) , or that the shots were fired by Polish soldiers in the confusion of the mass withdrawal . von Frentz claims that Polish troops and civilians massacred German civilians due to confusion . Polish historians feel the German historiography is based on Nazi German sources , ignoring numerous Polish sources . Polish historians , such as Madajczyk , Jastrzębski , Karol Marian Pospieszalski , Ryszard Wojan , and others claim that the killings were triggered when the ethnic Germans , dressed up as civilians , opened fire on the Polish troops . The Poles retaliated , killing many and executing prisoners afterwards . Polish historians like Pospieszalski and Janusz Kutta point to a Nazi top secret false flag Operation Himmler ( which took place on August 31 – September 1 ) and was designed to create an illusion of Polish aggression against Germany . Thus there is argument that actions like the Gleiwitz incident and events in Bydgoszcz were all part of a larger Nazi plan to discredit the Poles . Polish historians such as Pospieszalski and Wojan argue that the German fifth column agents ( or their higher - ups ) might have been deliberately aiming to produce a situation likely to result in German civilian casualties as a way to fuel Nazi propaganda . This argument has been criticized : Harry Gordon questions whether the Germans were willing to sacrifice their citizens for propaganda gains . In 2003 , the director of the Institute of History of the Academy of Bydgoszcz Wlodzimierz Jastrzębski reversed his earlier opinion on the subject . He said that there was no German diversion . Rather , Poles " lost their nerve " and vented their anger on helpless German civilians . Recent controversy . In 2004 , historian Tomasz Chinciński in a publication of Institute of National Remembrance ( IPN ) summarized recent research related to Bloody Sunday , confirming that the majority of historians agree that an " insurrection " by agents who had arrived from the Third Reich as well as some German inhabitants of Bydgoszcz took place . He has published a work detailing new evidence of German diversionary activity in September 1939 in Poland . There are numerous Polish eyewitness accounts of action of a German fifth column which included members of local minority ; Pospieszalski cited multiple witnesses for at least 46 cases of German civilians opening fire on Polish troops . There are numerous Polish Army reports and German documents confirming the saboteur actions of armed German Poles in other cities . According to German historians , any members of the fifth column , if present in the city , were infiltrators from Germany , not natives of Bydgoszcz . Eyewitness accounts have been criticised by Richard Blanke . In 2004 , Chinciński discussed previously unpublished reports of Polish Army Pomorze , which reported " a large scale diversion " in Bydgoszcz on September 3 and numerous smaller incidents in surrounding area around that time . A number of Polish and German historians discussed the problem September 4 , 2006 , at the German Historical Institute in Warsaw . Chinciński discussed newly discovered documents of the Abwehr that show that there were indeed plans for fifth column and diversion activities in Bydgoszcz ; he discussed the bias of the Polish communist era historiography , which minimized cases of Polish mob lynching of ethnic Germans , which did occur in Bydgoszcz . German historian Hans - Erich Volkmann noted problems with German historiography , outlining some of the unreliability inherent in early post - war studies , which were still significantly affected by the Nazi era , and that the Bydgoszcz events were and still are used for political purposes . Overall , German and Polish historians continue to argue with one another over the validity of their claims , but a consensus version is emerging .