Complex sentence: Donaldson received his officer commission in the Canadian Forces in the naval reserves in 1977 before joining the regular force in 1982 as a navigation specialist, before serving as a weapons officer, combat officer and executive officer.
Split into simpler sentences: Donaldson received his officer commission in the Canadian Forces in the naval reserves in 1977 before joining the regular force in 1982 as a navigation specialist. He then served as a weapons officer, combat officer and executive officer.