Spanish Service Barry served for four years as a marine in the Spanish Atlantic Fleet in the Irish company of Hugh Mostyn. In June 1605 his unit was transferred to the Army of Flanders to bolster the offensive led by Ambrogio Spinola, against the United Provinces of the Netherlands. Barry landed at Dunkirk (part of the Spanish Netherlands at the time) in December 1605. His unit joined the newly created Irish Tercio, commanded by Henry O'Neill, a younger son of Hugh O'Neill, Earl of Tyrone. Barry fought as a soldier at the siege of Rheinberg in 1608. Some time between 1610 and 1621 Henry died and was succeeded as maestre de campo by Shane O'Neill, who was however too young and Owen Roe O'Neill was acting commander. Tyrone died in far away Rome and in the eyes of the Spanish Shane O'Neill, the eldest surviving son, succeeded as Conde de Tyrone. His tercio became Tyrone's Tercio. Barry was promoted ensign in 1623. The tercio's maestre de campo, Henry O'Neill, died about 1626 and Owen Roe O'Neill succeeded in his post. Barry fought at the capture of Breda in 1624 and 1625. In 1628 he became captain in command of a company in Tyrone's Tercio. In 1632 he retired from active service. In about 1639 he returned to Ireland to recruit for the Army of Flanders. General of the Munster Army In October 1641 Phelim O'Neill launched the Irish Rebellion from the northern province of Ulster. When Barry visited Ireland in 1640 to recruit for the Spanish Army, his endeavour was interrupted by the arrival of the rebellion in Southern Ireland. Barry sided with his fellow Catholics. In January 1642 Barry and Maurice Roche, 8th Viscount Fermoy besieged Richard Boyle, 1st Earl of Cork in Youghal. On 2 March 1642 Donough MacCarty, the 2nd Viscount Muskerry joined the rebellion To resolve the rivalry between Muskerry and Fermoy, Barry was chosen as General of the insurgents' Munster army. In March 1642 Barry, Muskerry besieged William St Leger, the President of Munster, in Cork but weas driven off by Murrough O'Brien, 6th Baron Inchiquin, on 13 April. Barry then besieged King John's Castle in Limerick for the insurgents and took it through skillful use of the siege techniques he had learnt in Flanders—in particular undermining of the castle's walls (see Siege of Limerick 1642). The castle surrendered in June 1642. He then used