Crawford first went to sea aboard merchant vessels, trading with North America, before joining the navy during the American War of Independence.

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.

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.

[1][2] He initially went to sea aboard merchant ships, making several voyages to trade with the American colonies of Virginia and North and South Carolina, before joining the navy in April 1777.

[3] His first posting was as a midshipman aboard the sloop HMS Vigilant, then serving off the North American coast under the command of Lieutenant John Henry.

[1] Crawford took part in several important battles during the remainder of the war, commanding a battery of Fowey's guns that had been landed to defend Savannah during its siege.

The Spanish sent 14 gunboats from Algeciras to attack her, against which the senior British officer, Roger Curtis, dispatched Crawford's Repulse, and another armed vessel, the Vanguard, to defend her.

[4] After thirteen months commanding Repulse, often closely engaged with Spanish gunboats, Crawford was appointed acting first lieutenant of the 32-gun HMS Brilliant.

Anticipating the assault, and the danger to shipping, the British scuttled Brilliant, and Crawford went ashore to serve with the naval brigade encamped at Europa Point under Curtis.

He remained her until October 1782, when he was moved to the recently captured Spanish ship of the line San Miguel, which had run aground off Gibraltar and forced to surrender.

San Miguel was eventually sailed to Britain under the command of Sir Charles Knowles, and Crawford joined Roger Curtis aboard the Brilliant in March 1783.

The crisis passed without breaking into open war, and Crawford took a period of absence from the navy, going out to the East Indies where he attended to his personal affairs.

Once there he was appointed lieutenant aboard the 98-gun HMS Prince, which was at this time the flagship of Crawford's old patron, now Rear-Admiral Sir Roger Curtis, with the Channel Fleet.

[10] During operations off Vigo Crawford arranged for the capitulation of the French garrison of the fort there, which caused his senior officer to write approvingly of his "liberal attention and zealous services".