During Stalin's Great Terror in the Soviet Union, a major ethnic cleansing operation, known as the Polish Operation, took place from about 25 August 1937 through 15 November 1938. According to Soviet NKVD archives, 111,091 Poles, and people accused of ties with Poland, were executed, and 28,744 were sentenced to Gulag labor camps, for a total of 139,835 Polish victims. This number constitutes 10 per cent of the officially persecuted persons during the entire Yezhovshchina period, with confirming NKVD documents. The prosecuted Polish families were accused of anti-Soviet activities.