Complex sentence: Upon completion of this tour of duty, he returned to Langley Field, Virginia, where he became the engineering and armament officer of the 49th Bombardment Squadron, 2nd Bombardment Group, in December 1934.
Split into simpler sentences: Upon completion of this tour of duty, he returned to his duties at Langley Field, Virginia. He became the engineering and armament officer of the 49th Bombardment Squadron at Langley, in December 1934.