Castlehaven was involved in the defence of Ireland during the
Confederate Wars of the 1640s and in the subsequent Cromwellian invasion. During the outbreak of the
Irish uprising in 1641–42, Castlehaven volunteered to help suppress the Irish rebels, but because he was a Catholic he was not trusted to take command. Shortly afterwards, he was arrested and detained at
Dublin Castle. Fearing that he would meet the same fate as the
Earl of Strafford, Tuchet manage to escape 27 September, with the help of a friend and fled south into the
Wicklow Mountains. His intention was 'to gain a passage by Wexford into France, and from thence into England;’ but coming to Kilkenny, the headquarters of the confederate Catholics, he was persuaded to accept a command in the army, and was appointed general of horse under Sir
Thomas Preston, 1st Viscount Tara. It was believed among the northern Irish that his escape was a contrivance on the part of the
Earl of Ormonde 'to work an understanding' between him and his kindred in rebellion, Castlehaven being related to him through the marriage of his sister with Edmund Roe Butler. Even though he considered himself English, he was appointed a member of the 25-strong Supreme council of the
Confederation of Kilkenny. In 1644 the Irish Confederate Supreme Council decided to vote for Castlehaven as the commander of a 6,000-strong expedition force in a push against the Ulster-Scottish army under
Robert Monro. The campaign under Castlehaven proved indecisive, the large army being mostly used to defend the stronghold of
Charlemont. Historians generally consider the expedition to have been a wasted opportunity: as a result of this,
Owen Roe O'Neill considered Castlehaven to be incompetent and
Thomas Preston also developed a dislike of him. (Castlehaven somewhat unconvincingly later blamed O'Neill for the failure of the expedition). However, Castlehaven was not entirely lacking in military ability. Apart from Owen Roe O'Neill, he proved to be the only Irish Confederate commander capable of winning conventional set-piece battles. In 1643 he surprised and routed hundreds of Inchiquin's men in county Cork at the
battle of Cloughleagh. In 1650 he won a second small (though inconsequential) victory over an English
Parliamentarian force during the
battle of Tecroghan with some aid from
Ulick Burke. The great weakness of Castlehaven was that he was largely an amateur, lacking the patience to conduct sieges and somewhat touchy- it is said that some referred to him as
Tiarna Beag or 'Little Lord.' The anonymous author of the Aphorismical Discovery, a contemporary account of events during the Confederate wars in Ireland, contemptuously referred to Castlehaven as the 'pigmeyan Goliath of Clanricarde.' == Later years ==