Crawford first went to sea aboard merchant vessels, trading with North America, before joining the navy during the American War of Independence. He saw action on shore on several occasions, distinguishing himself in the defence of Savannah and the siege of Charleston. Returning from North America with despatches, he was given a hired ship and acted in support of the British defences during the Great Siege of Gibraltar. During this conflict he was heavily engaged on numerous occasions with Spanish gunboats, and came to the attention of Roger Curtis, later to become a prominent naval officer. After a period of unemployment following the end of the American War of Independence, Curtis saw to it that Crawford was offered a position in the fleet during the Spanish Armament. When war was averted, Crawford went out to the East Indies for several years on personal business.