In 1755, Strachan was appointed second lieutenant aboard the 98-gun HMS St George, which was then the flagship of Lord Hawke.
The following year Strachan accompanied Hawke to Gibraltar aboard HMS Antelope, to relieve John Byng.
[1] During the encounter Strachan came alongside and sent a boarding party onto the Télémaque under William Locker, who secured her surrender.
In 1770 Strachan was appointed to command HMS Orford, one of the squadron which went with Rear-Admiral Robert Harland to the East Indies.
[1] After his death the baronetcy passed to his nephew, Richard John Strachan who also became a distinguished Navy officer.