[3] From 1675 Dorrington gained experience as a Captain in a regiment of Anglo-Irish volunteers under the command of the Duke of Monmouth, serving with the French Army of Louis XIV in their war against the Dutch.

[9] Dorrington remained loyal to James during the Glorious Revolution of 1688, when a majority of senior officers in England defected to the invading force of William of Orange.

Dorrington was formally appointed as colonel of the Foot Guards, succeeding the Protestant Duke of Ormonde, and eventually became one of six Major-Generals of the Jacobite army.

The 1691 campaign opened with a brief but bloody siege at Athlone; while the Williamite army took the town, the main Jacobite force fell back along the Galway road.

[14] In late 1693 he submitted a petition complaining about his treatment, having been denied rights usually given to prisoners of war; Lucas, the governor of the Tower, was later reprimanded for his "ill-usage" of Dorrington.

[14] The London Gazette advertised a reward of £300 for his capture, describing him as a "a tall spare Man, aged near 50 or thereabouts, thin Visaged, having a Welt near the lower part of his Right Cheek by a Shot".

Following the Peace of Ryswick which ended the war, the Foot Guards were amalgamated into the Irish Brigade of the French Army as Dorrington's Regiment.