From the beginning of the German-Soviet War he served on the Leningrad Front with 153 IAP as a Leytenant and was later promoted to Starshiy Leytenant and Flight commander. In 1941 he claimed 7 victories in 189 missions. Piloting a Polikarpov I-153 biplane, he shot down a future high-scoring German ace Lt. Walter Nowotny of JG 54 over Saaremaa on 19 July 1941 in Bf 109 E-7 (W.Nr. 1137) "White 2" over Riga Bay. In that fight Avdeyev's plane was also shot down and he subsequently spent a month in hospital due to injuries sustained during the crash.