In their attack, the Red Army overrun 52.1% of territory of interwar Poland with over 13,700,000 inhabitants. The Soviet occupation zone included also 336,000 new refugees who escaped from Polish lands invaded by Germany, numbering at around 198,000. Spreading terror throughout the region, the Soviet secret police (NKVD) accompanying the Red Army massacred Polish prisoners of war, and in less than two years, deported up to 1.5 million ethnic Poles to Siberia including Poles and Polish Jews from West Belarus. Twenty-one months after the Soviet invasion of Poland, during the German Operation Barbarossa of June 1941, West Belarus was overrun again by the Wehrmacht followed closely behind by Einsatzgruppen and the mass executions of Polish Jews commenced.