Complex sentence: As Mynarski approached the escape hatch, he saw that his close friend, the rear gunner, Pilot Officer Pat Brophy, was trapped in his turret and immediately made his way through the flames to his assistance, but all his efforts were in vain.
Split into simpler sentences: As Mynarski approached the rear escape hatch, he saw that his close friend, the tail gunner, Pilot Officer Pat Brophy, was trapped in his turret. Mynarski immediately made his way through the flames to Brophy's assistance, but all his efforts were in vain.