Complex sentence: His most famous battle was when his unit of around 150 men killed total of 19 Navy Seals three in Operation Red Wing and an additional 16 Seals died trying to rescue the four Navy SEALs who started the Red Wing mission.
Split into simpler sentences: His most famous battle was when his unit of around 150 men killed three Americans in Operation Red Wing. An additional 16 men died trying to rescue the four Navy SEALs who started the Red Wing mission.