Career
He was instrumental in the creation of German Democratic Republic, and served as the first Soviet ambassador to East Germany. 1938 — Semyonov begins work for the Ministry of Foreign Affairs (MID)
1939—1940 — an advisor of Soviet Plenipotentiary Representation in Lithuania
1940—1941 — a counsellor of the Soviet Embassy in Nazi Germany
1941—1942 — an executive of the Third European Department of the MID
1942—1945 — a counsellor of the Soviet Mission in Sweden
1945—1946 — a deputy of the a Political Counsellor of the Soviet Military Administration in Germany
1946—1949 — a Political Counsellor of the Soviet Military Administration in Germany
1949—1953 — a Political Counsellor of the Soviet Control Committee in Germany
1953—1954 — Chief Commissar of Union of the Soviet Socialist Republics in Germany and an ambassador to the German Democratic Republic;
1954—1955 — an Executive of the Third European Department of the Ministry of Foreign Affairs
1955—1978 — Deputy Minister of Foreign Affairs
1968–1978 - Chief of the Soviet delegation at the Soviet-American negotiations on reduction of strategic weapons in Helsinki, Vienna, Geneva. Prepared the 1973 Strategic Arms Limitation Talks-1 and 1978 Strategic Arms Limitation Talks-2 Treaties for signing by General Secretaries Leonid Brezhnev and Presidents Gerald Ford and Jimmy Carter.
1978—1986 — Union of the Soviet Socialist Republics ambassador to West Germany
1986–1991 — the Foreign Ministry Ambassador at Large, Counsellor to the Foreign Minister.