Anti-Jewish massacres in eastern Poland in 1941
Immediately following the German invasion of the Soviet Union in June 1941, anti-Jewish pogroms occurred in at least 219 localities in the lands that had been part of Poland prior to 1939 and were occupied by the Soviet Union from 1939 to 1941. 
Background.
According to political scientists Jeffrey Kopstein and Jason Wittenberg, the presence of a political threat is the strongest explanatory factor for why pogroms occurred in some locations but not others: "Pogroms were most likely to occur where there were lots of Jews, where those Jews advocated national equality with non-Jews, and where parties advocating national equality were popular." 
Pogroms.
Anti-Jewish pogroms occurred in at least 219 localities in the eastern borderlands of Poland, i.e. lands that had been part of Poland prior to 1939 and were occupied by the Soviet Union from 1939 to 1941. Among these pogroms were the Jedwabne pogrom, Lviv pogroms (1941), Szczuczyn pogrom, and Wąsosz pogrom. Kopstein and Wittenberg estimate around twenty-five thousand to fifty thousand "deaths resulting from neighbor-on-neighbor violence in summer 1941", significantly less than the 1918–1920 pogroms in Poland.
Kopsten and Wittenberg also write that "Yet pogroms were relatively rare events." The 219 pogroms represent "just 9 percent of all localities in the region where Jews and non-Jews dwelled together. Most communities never experienced a pogrom and most ordinary non-Jews never attacked Jews".
References.
 ;templatestyles src="Reflist/styles.css" / ;