He was selected to be chief of staff of the 3rd Guards Tank Army in the order forming it оn 14 May and was promoted to major general of tank forces on 7 June. The army fought in Operation Kutuzov as part of the Bryansk Front from July. From September the army fought in the Battle of the Dnieper, the Battle of Kiev, the Zhitomir–Berdichev Offensive, and the Proskurov–Chernovitsy Offensive. As chief of staff of the army, Mitrofanov was evaluated as having "taken an active role in the planning of army operations, ensuring unbroken command and control of forces in accordance with the decisions of the army commander," and "displaying excellent staff education and knowledge of operational art." He became army deputy commander in May 1944 and took command of the army's 7th Guards Tank Corps in July after its commander was wounded. Mitrofanov led the corps in successful attacks during the Lvov–Sandomierz Offensive, in which it captured Gorodok and Lvov, and fought in battles for the Sandomierz bridgehead. For its courage and skill in these battles, his corps was awarded the Order of Suvorov.