In the Thirteen colonies, Britain recruited German and Swiss immigrant settlers as soldiers for the regiment after General Edward Braddock's defeat in 1755 in western Pennsylvania in the French and Indian Wars.
After recovery, in 1761 Jacques Marcus traveled with Henry Bouquet, a Swiss colonel in the Royal American Regiment, to set up a British post at Presque Isle (present-day Erie, Pennsylvania).
Prevost was next assigned to command a body of troops in New York City; after Britain defeated France and military activity was reduced, he was put on half pay.
While Jacques was away fighting for the British in the West Indies, his wife Theodosia formed a relationship with an American colonel named Aaron Burr, who was ten years younger than her.
In 1781, soon after learning of her husband's death, the newly widowed Theodosia got remarried to the young Burr, who adopted the Prevost family's five children.
He fought against Native American forces in the Muskingum River Valley of present-day Ohio, returning to Theodosia in New York in 1765.
Jaques Marcus Prevost led British troops at the Battle of Brier Creek, a rout of the Americans that reversed their momentum and delayed the eventual outcome by a year.