Complex sentence: Two days later, on August the 1st, he claimed his final victory on the Mius Front-a LaGG-3 that was, most probably, the Yak-1 flown by Soviet female ace, Lydia Litvyak.
Split into simpler sentences: Two days later, on August the 1st, he claimed a LaGG-3 on the Mius Front. Actually that aircraft was, most probably, the Yak-1 flown by Soviet female ace, Lydia Litvyak.