A colonel in the army, he was a prominent figure in the Irish Rebellion of 1641 and afterwards defended against the Cromwellian conquest of Ireland as Governor of the Castles of Antrim and Toome.
His home outside Stewartstown, County Tyrone - Irry, sometimes also spelt Eary - was later renamed Stuart Hall by his grandson, the 7th Baron Castle Stewart.
Stewart was duly appointed an officer in the rebel forces by his wife's cousin, the leader of the rebellion, Sir Felim O'Neill of Kinard.
[2] His early activities against the victorious English miraculously managed to escape their notice until twelve years later, by which time he had become a loyal servant of Parliament.
He defended both forts until the final settlement of Ireland under Oliver Cromwell in 1649, when he was forced to capitulate on honourable terms to General Robert Venables.