The Irish Jacobite army was the largest body of Irish soldiers ever to go into battle prior to the twentieth century. Although largely a new force, for three years, in alliance with France, it sustained a major war against a multi-national and more professional Williamite army, involving pitched battles, sieges and other military operations throughout Ireland. This book outlines the course of the war, but primarily its focus is on a detailed examination of the army's various aspects. The coverage includes the army's peacetime origins; its reaction to the 1688 revolution; descriptions and analysis of the infantry, cavalry, artillery and engineering corps, and of the legal, medical and chaplaincy services. There is treatment of the army's command and staff structure, its finance and logistics, the French dimension and the roles of various auxiliary forces that supported it. The backgrounds and beliefs of its personnel are also considered. Many of the army's personalities are introduced. The army's eventual fate and its lingering tradition on the continent are described.