Immediately upon the German invasion of the Soviet Union, Kovachevich and the rest of his regiment began flying sorties to defend the Moscow region. On 11 October 1941 he shot down his first enemy aircraft, a Bf 109, after which he quickly increased his tally of aerial victories. Having participated in the battle for Moscow, he went on to fly the La-5 in the Battle for Stalingrad until being transferred to the 9th Guards Fighter Aviation Regiment as a squadron commander. By then he had already tallied thirteen solo aerial victories, for which he was nominated for the title Hero of the Soviet Union in February 1943, which he received on 1 May that year. He continued to fly in combat, and was wounded during a mission, but remained in the regiment and continued active service upon recovery. During the battle for Crimea he was promoted to assistant commander for flight training, and subsequently deputy regimental commander in April 1944. After the death of regimental commander Anatoly Morozov in June he was made acting commander, but held the position only briefly before being sent to study at the Air Force Academy and replaced by Vladimir Lavrinenkov. Throughout the course of the war he totaled 20 solo and 7 shared shootdowns accumulated over the course of roughly 520 sorties, piloting the MiG-3, La-5, Yak-1, and P-39 fighters.