The Soviet Union invaded Poland in September 1939 under the Molotov–Ribbentrop Pact with Germany; the Soviet Union invaded Finland in November 1939; in June 1941, Germany abrogated the non-aggression pact and invaded the Soviet Union. Although the USSR had outstanding scientists and engineers, began research on what would later become radar ("radiolokatsiya", lit. radiolocation) as soon as anyone else, and made good progress with early magnetron development, it entered the war without a fielded, fully capable radar system.