The 23-mm Vja cannon was replaced with 1 or 2 N-37 or P-37 37-mm cannon on the -2m3. Most favored battle field tactic was for attack unit to cross enemy lines and form "race track" pattern and attack enemy armored units from rear. Attacking aircraft would stay in this pattern until ground units were destroyed or ran out of ordnance. In one attack against 17th Panzer Division, Shturmoviks destroyed 240 of estimated 300 tanks in 4-hr assault. Bravery of Russian pilots was major factor in success of Shturmovik.