Complex sentence: Gerry remained in the USAF Active Reserve until 1964 attaining the rank of Captain, then the USAF Inactive Reserve until 1974 when he was retired from the USAF Reserve.
Split into simpler sentences: Gerry remained in the USAF Active Reserve until 1964 attaining the rank of Captain. He was then assigned to the USAF Inactive Reserve until 1974 when he was retired officially from the USAF Reserve.