Complex sentence: In 1966, Levin was forced to leave the performing version of the Raiders when the draft beckoned; to avoid a combat assignment, he joined the National Guard, which enabled him to record with the group during his time off.
Split into simpler sentences: In 1966, Levin was forced to leave the performing version of the Raiders when he was called up for the draft. This enabled him to record with the group during his time off.