Semyon Timoshenko, who had been named People's Commissar for Defence of the Soviet Union after the debacle of the Winter War and was in urgent need of experienced officers to fill command posts for the rapidly expanding Soviet army, returned Rokossovsky to the command of the 5th Cavalry Corps at the rank of colonel. Subsequently, the 5th Cavalry Corps participated in the occupation of Bessarabia and he was soon promoted to the rank of a major general and given the command of the 9th Mechanized Corps, as part of M.I. Potapov's 5th Army under Mikhail Kirponos commander of the Kiev Military Region, which would later be renamed the Southwestern Front at the outbreak of hostilities with Germany.