Strengthening the defense capability of our country occupied one of the main places in the work of the outstanding Soviet aircraft designer, Academician Sergei Vladimirovich Ilyushin, and his design activity in the pre-war years was entirely devoted to solving this problem. The vast practical experience acquired during his service in the Air Force, and then work in the aviation industry, a deep and comprehensive study of the strategy and tactics of the combat use of aircraft and, finally, the scientific foresight of the designer allowed him, contrary to the prevailing military doctrine at that time, draw an important and correct conclusion about the main purpose of aviation in the coming war - full support for the actions of ground forces. The idea of creating a battlefield aircraft, an attack aircraft, was far from new. But simultaneously with its appearance, insoluble contradictions arose, the essence of which was the desire to install powerful weapons, reliable armor on such an aircraft and at the same time obtain high flight and combat qualities.