Military career
In late 1739, the Parliament of Great Britain decided to raise a regiment of foot in British North America to serve against Spain at part of the War of Jenkins' Ear. The regiment, to be composed of four battalions, was designated Gooch's American Regiment. The company commanders were to be recruited in the colonies and Colonel William Blakeney was sent across the Atlantic with blank commissions, signed by King George II, to be distributed to the various governors. On 10 July 1740, Lieutenant Governor of Virginia William Gooch awarded the senior (of 4) Captain's Commission in one of Virginia's companies to Lawrence Washington: his Commission survives in the archives of the Mount Vernon estate.
The four Virginia Companies mustered at Williamsburg, Virginia, in August 1740, but the transport ships did not set sail for Jamaica until early October. The main British invasion force did not arrive in Jamaica until early January 1741, and the Conjunct Expedition, under the dual command of Vice Admiral Edward Vernon and Brigadier General Thomas Wentworth, got under way in late January. In early February, commanders decided to assault the Spanish fortress at Cartagena in present-day Colombia. At that time, some of the Americans were seconded to Admiral Vernon's warships to be used as Marines. Lawrence was fortunate, as he would later write to his father, to be appointed "Captain of the Soldiers acting as Marines" on board Vernon's flagship, the 80-gun HMS Princess Caroline. Because of this service, the 43rd Foot was called "Gooch's Marines."
Washington survived the Battle of Cartagena de Indias and expeditions against the seaport of New Granada and against Cuba and Panama, which suffered a high rate of casualties, mostly from disease. The assault against Cartagena, in March–April 1741, proved a disaster, as over half of the British force fell ill and died of tropical diseases, chiefly yellow fever. The fever predominated amongst the newly arrived troop ships, while the crews on Vernon's warships, having already been in the Caribbean for one year, were largely inured against disease. Washington survived the fevers which killed off nearly 90 percent of the American colonists because of his fortunate (early) transfer from a troop ship to Vernon's flagship, which, having been in the tropics for over one year, had a crew already inoculated against tropical diseases (as well as less crowded conditions aboard ship.)
In January 1741, some 3,255 officers and men of Gooch's "American Regiment" were on board ship in the harbor of Kingston, Jamaica. Not quite two years later, on 24 October 1742, the American survivors could muster only 17 officers and 130 enlisted men, who returned to North America in November and December, accompanied by 268 sick soldiers. On 17 January 1743, The New York Weekly Journal contained a dispatch from Jamaica dated 24 October 1742:
from Jamaica, we are informed that General Wentworth had received Orders to return to Great Britain with his British Forces and to reduce [disband] the American Regiment under Colonel Gooch. Each man is to be paid to the 24th of October and sent home on four transports, viz: one to New York, two to Virginia, and one to North Carolina. A very melancholy reflection that of the five hundred men sent from this Province in five vessels at the first embarkation.
Writing a history of British Settlements in North America in 1748, Bostonian Dr. William Douglas said that of 500 men sent from Massachusetts for the expedition, not over 50 returned.
Washington also participated in the 1741 British landing at Guantanamo (Cumberland Harbor) Cuba, part of Admiral Vernon's plan—never realized—to attack Santiago de Cuba from the rear (by land) and from the front (by sea).
Upon his return to Virginia at the end of 1742, Washington discovered that the post of militia commander, Adjutant, was vacant. He applied for it and was appointed Adjutant, at the rank of Major, by Governor Gooch in Spring 1743.