Kozlov remained behind the enemy's lines and was appointed chief of the Voblast's underground Communist Party in July.

He was tasked with organizing resistance activities, and led the Minsk partisans until the end of the German occupation.

[6] As commander of one of the occupied republic's largest partisan detachments, he was given the rank of a Major General on 16 September 1943.

Kozlov remained the chairman of the Minsk Voblast's Communist Party regional committee, an office he held for four further years.

[10] In addition, he was a candidate member of the Communist Party of the USSR's Central Committee during its 20th, 21st and 22nd convocations, from 25 February 1956 to 29 March 1966.