East and West Prussia voted in a plebiscite to become part of Germany, though a section of West Prussia would be handed to Poland to provide a 'Polish Corridor': The East Prussian plebiscite dealt with the issue of self-determination of the regions southern Warmia (Ermland), Masuria (Mazury, Masuren) and Powiśle, which had been in parts of the East Prussian Government Region of Allenstein and of West Prussian Government Region of Marienwerder, and was to be held in accordance with Articles 94 to 97 of the Treaty of Versailles. The German side engaged in mass persecution of Polish activists, their Masurian supporters, hunted them down and murdered them to influence the vote. Poles boycotted the preparations for the plebiscite, which was tampered with by the Germans in an effort to manipulate the results.. The German conducted plebiscite reported a majority of voters selected East Prussia over Poland (over 97% in the Allenstein Plebiscite Area (de) and 92% in the Marienwerder Plebiscite Area (de); most of the territories in question remained in the Free State of Prussia, ie, in Germany.
In Jazłowiec, the 14th Regiment of Jazłowiec Uhlans celebrated its Day. The Regiment was a cavalry unit of the Polish Army in the Second Polish Republic, and named after the village of Jazlowiec where in July 1919, they fought one of the battles of the Polish-Ukrainian War. They were stationed in Lwow in the interbellum period, and were a unit in the Polish Armed Forces in the West, and the Home Army during WW2.
Bloody Sunday, the beginning of Massacres of Poles in Volhynia and Eastern Galicia: OUN-UPA death squads aided by the local Ukrainian peasants simultaneously attacked at least 99 Polish settlements within the Wołyń Voivodeship of the prewar Second Polish Republic under the German occupation. It was an orchestrated attack on people gathered for a Sunday mass at Catholic churches.The towns affected included Kisielin (Kisielin massacre), Poryck (Poryck Massacre), Chrynów (Chrynów massacre), Zabłoćce, Krymn, with dozens of other towns attacked at different dates with tens of churches and chapels burned to the ground. The Volhynian massacres spread over four prewar voivodeships including Wołyń with 60,000 victims, as well as Lwów, Stanisławów and Tarnopol in Lesser Poland with 70,000 Poles murdered for the total of 130,000 Polish victims of UPA terror. The Bloody Sunday of July 11, 1943, is not to be confused with the Stanisławów Ghetto Bloody Sunday massacre of 10,000 to 12,000 Polish Jews on October 12, 1941, before the Stanisławów Ghetto announcement.
Zagaje massacre: Troops of the Ukrainian Insurgent Army group "Piwnicz", aided by Ukrainian peasants, massacred ethnic Poles - about 260 to 350 men, women, and children. The village Zagaje was leveled out and does not exist anymore. It was located in the gmina Podberezie of the Horochów County in the Wołyń Voivodeship of the Second Polish Republic (now, Horokhiv Raion, Ukraine)
Gurów massacre: The Ukrainian Insurgent Army death squad from Group "Piwnicz"and Ukrainian peasants launched a massacre of the Polish citizens in the town of Gurow. It took place during the Massacres of Poles in Volhynia and Eastern Galicia. Gurów was located in Gmina Grzybowica, Powiat Włodzimierz in the Wołyń Voivodeship of the Second Polish Republic. The town no longer exists. Of the 480 Polish citizens of Gurów about 70 people managed to escape death by hiding from the attackers. Historians Władysław and Ewa Siemaszko have confirmed by name the 200 Poles and 2 Jews murdered in Gurow. The killing spread to other nearby towns - Wygranka, Zdżary, Zabłoćce, Sądowa, Nowiny, Zagaje (see Zagaje massacre), Poryck (see: Poryck massacre), Oleń, Orzeszyn, Romanówka, Lachów, and Gucin.
Wilhelm Koppe, an SS-Obergruppenführer and head of the Höhere SS und Polizei Führer, was wounded on July 11, 1944 in Kraków in a plot code-named Operation Heads (Glowki). The Operation consisted of several Nazi officers targeted for assassination, and was carried out by members of the Polish Resistance. Nazi German officers were sentenced to death by the Special Courts of the Polish Underground for crimes against Polish citizens during the World War II occupation of Poland. The name of the operation, "Operation Heads" was a sarcastic reference to the Totenkopf (Gr. 'skull') 'Death's Head' symbol of SS Nazi German uniforms and headgear.