This book assesses the service of Henri de Ruvigny, later earl of Galway, in France until the revocation of the edict of Nantes in 1685, his central role in transforming Ireland in the aftermath of the Glorious Revolution, and his service of the British monarchy as administrator, military commander and diplomat. The analysis rests on underutilized sources in French, shedding light on a hitherto overlooked civil servant in this crucial period of Irish and British history, wrought with constitutional crises, but also on the Protestant International and the lesser-known fronts of the war of 1689-1697.