Among the mechanized corps (MC), four formations were especially well equipped. On the day of German invasion, about 70% of the total T-34 and KV tanks produced at that time were deployed in the 4th, 6th, 8th, and 15th MC. The 6th MC operated in the Białystok area, and all of the others in the Soviet Ukraine. All of their engagements with German tanks happened during or just before the Battle of Brody: