Protecting the Empire's Frontier tells stories of the roughly eighty officers who served in the 18th (Royal Irish) Regiment of Foot, which served British interests in America during the crucial period from 1767 through 1776. The Royal Irish was one of the most wide-ranging regiments in America, with companies serving on the Illinois frontier, at Fort Pitt, and in Boston, New York, and Philadelphia, with some companies taken as far afield as Florida, Spanish Louisiana, and present-day Maine. When the regiment was returned to England in 1776, some of the officers remained in America on staff assignments. Others joined provincial regiments, and a few joined the American revolutionary army, taking up arms against their king and former colleagues.

Using a wide range of archival resources previously untapped by scholars, the text goes beyond just these officers' service in the regiment and tells the story of the men who included governors, a college president, land speculators, physicians, and officers in many other British regular and provincial regiments. Included in these ranks were an Irishman who would serve in the U.S. Congress and as an American general at Yorktown; a landed aristocrat who represented Bath as a member of Parliament; and a naval surgeon on the ship transporting Benjamin Franklin to France. This is the history of the American Revolutionary period from a most gripping and everyday perspective.

An epilogue covers the Royal Irish's history after returning to England and its part in defending against both the Franco-Spanish invasion attempt and the Gordon Rioters. With an essay on sources and a complete bibliography, this is a treat for professional and amateur historians alike.