Hugh Mercerstudied medicine at Marischal College, Aberdeen. He became assistant surgeon in Bonnie Prince Charlie's Army. After the defeat at Culloden he was a fugitive in Scotland for many months before buying a passage to America, where he set up practice.

In 1755 he joined the British army as a soldier not a doctor and rose to the rank of colonel. He befriended another colonel, George Washington, and in 1776 joined the American Revolutionary Army. He was promoted to Brigadier General and died from wounds received in a battle with the British in January the following year.

His efforts contributed to Washington's ultimate victory and he is remembered in America by many places being named after him. He is commemorated by a plaque in the Quadrangle, Marischal College, Aberdeen.