 Complete the following phrase:  Polish historians, such as Madajczyk, Jastrzębski, Karol Marian Pospieszalski, Ryszard Wojan, and others claim that the killings were triggered when the ethnic Germans, dressed as civilians, opened fire on the Polish troops Jastrzebski later changed his views after starting to work with German expelee organizations. 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 it is argued that actions like the 