The Polish government in exile in London during World War II received sensitive military information about Nazi Germany from agents and informants throughout Europe. After Germany conquered Poland in the autumn of 1939, Gestapo officials believed that they had neutralised Polish intelligence activities. However, certain Polish information about the movement of German police and SS units to the East during the German invasion of the Soviet Union in the autumn of 1941 was similar to information British intelligence secretly obtained through intercepting and decoding German police and SS messages sent by radio telegraphy.[36]