 The trials conducted by the <unk> VVS included engagements between the Tu @-@ 12 and the Soviet <unk> @-@ 9 and <unk> @-@ 23 jet fighters which were very useful in evaluating the offensive armament of the fighters , the defensive armament of the bomber and the proper tactics involved for both types of aircraft . The tests demonstrated the <unk> of the current 12 @.@ 7 mm ( 0 @.@ 50 in ) armament and meant that every Soviet bomber <unk> would have a defensive armament using power @-@ operated turrets that carried guns 20 mm or larger . 
