Complex sentence: By late August 1943, Hartmann had ninety aerial victories, but, on 19 August, in combat with Il-2s, his aircraft was damaged by debris, and he was forced to land behind Soviet lines.
Split into simpler sentences: By late August 1943, Hartmann had ninety aerial victories. On 19 August, in combat with Il-2s, his aircraft was damaged by debris, and he was forced to land behind Soviet lines.