Baillie entered the navy about 1740, and was made lieutenant on 29 March 1745. In 1756 he was serving on board the 60-gun , and was present at the action near Minorca on 20 May. He was shortly afterwards promoted to the command of the 12-gun sloop , and early in the following year, whilst acting captain of the 28-gun , captured a French privateer of 24 guns and 240 men, which was purchased into the service as . Baillie was promoted to post captain and appointed to command her on 30 March 1757. In this ship he continued, engaged for the most part in convoy service, till she was lost in 1760; and in the following year, 1761, he was appointed to Greenwich Hospital, through the interest, it is said, of the Earl of Bute; he certainly had no claim to the benefits of the hospital by either age, or service, or wounds.