After signing the Molotov-Ribbentrop Pact in 1939, the Soviets invaded Poland and took part in its dismemberment. The Soviet authorities declared Poland to be nonexistent, and all former Polish citizens from the areas annexed by the Soviet Union were treated as Soviet citizens. That resulted in the arrest and imprisonment of approximately 2 million Polish citizens (including a quarter of a million prisoners-of-war and 1.5 million deportees) by the NKVD and other Soviet authorities.