As the pro-Soviet and communist controlled Polish armed forces were being formed in the Soviet Union, in June 1943 Ochab joined the 1st Tadeusz Kościuszko Infantry Division and was enlisted as a political officer with the rank of second lieutenant. In October 1943 he fought valiantly in the Battle of Lenino, for which he was decorated with both the Polish and Soviet medals for valor. In the summer of 1944 Lieutenant Colonel Ochab was already a member of the Central Committee of the Polish Workers' Party.