[1] In early 1945, after 5 months of officer training in the Soviet Union, he was commissioned a lieutenant in the Soviet-allied Polish People's Army.

In the army he became a "political officer"; he advanced also in the PPR and then the Polish United Workers' Party (PZPR).

From 1951 to 1953 he underwent a Command-and-Staff course for Brigade and Division Command at the M. V. Frunze Military Academy in the Soviet Union.

[3] Siwicki was a long-serving Minister of National Defense in the governments of Wojciech Jaruzelski, Zbigniew Messner, Mieczysław Rakowski and Tadeusz Mazowiecki (from 1983 to 1990 total).

[6] As agreed in the Round Table talks and during subsequent political developments, Siwicki remained the Minister of Defense in Solidarity-led government of Mazowiecki until July 1990.