Complex sentence: He achieved the rank of captain in 1942 and was promoted to major in 1943, before he was classified medically unfit for overseas service, and was confined to staff work in Australia, where he was quartermaster for the Australian II Corps and the Australian Second Army.
Split into simpler sentences: He achieved the rank of captain in 1942 and was promoted to major in 1943, before he was classified medically unfit for overseas service. He was confined to staff work in Australia, where he was quartermaster for the Australian II Corps and the Australian Second Army.