Complex sentence: In April 1942, Lieutenant-Colonel Jimmy Doolittle and his crew had crash-landed in China after the Tokyo raid--they launched from an aircraft carrier, but flew from Tokyo to China because of lack of fuel, planning to land as best they could.
Split into simpler sentences: In April 1942 Lieutenant-Colonel Jimmy Doolittle and his crew crash-landed in China after the Tokyo raid. They had taken off from an aircraft carrier, but flew from Tokyo to China because of lack of fuel, planning to land as best they could.