On September 26, 1939, a Soviet aircraft dropped anti-Polish propaganda leaflets, which stated that "Poles are not capable of self-governing their country," so "the Soviets come to take care of them out of mercy." Soon afterwards the city was turned over by the Germans to the Red Army, which entered on September 29. The Soviets established a local station of the NKVD, and the Polish population was subjected to various repressions. In January 1940, the Soviets changed several street names, even calling one "September 17 Street", after the day of the Soviet invasion of Poland. At least 32 Poles from Łomża were murdered by the Russians in the Katyn massacre in 1940. The Soviets carried out arrests of the Capuchin monks and expelled Benedictine nuns in mid-1940. According to Soviet data from September 1940, over 330 Polish families were deported from the district to the USSR. In 1941 the local Polish underground resistance movement was weakened when the Soviets arrested its commander. The Soviets held 2,128 people in the local prison as of June 21, 1941, the day before Germany invaded the Soviet Union, and on June 20–21 they carried out mass deportations of Poles to Russia. Łomża remained under Soviet control until Operation Barbarossa.