(1717–78) military engineer who came to America (in 1754) with a British unit at the time of the French and Indian War (1754–63). Mackellar built roads and bridges in the wilderness (1755), but his flawed maps contributed to Gen. Edward Braddock's loss at Monongahela (1755). He was also present at the capitulation of Fort Oswego (1756) and the capture of the fortress at Louisbourg (1758). Mackellar was chief engineer in the expedition against Quebec (1759) and later at the Halifax citadel (1760) before taking part in the expedition against Martinique (1762) and conducting siege operations against Havana (1762).
From The Oxford Essential Dictionary of the U.S. Military in Oxford Reference.
Subjects: Warfare and Defence.