Maurice, Earl of Kildare, suppressed the insurrection in 1339 of the O'Dempsies in Leinster; and in November 1346, with Lord Justice Bermingham, forced the O'Mores to submit and give hostages for their future good behaviour.
On 26 January 1347 he was summoned by Writ signed at Eltham Palace to serve King Edward III at the siege of Calais where he proceeded in May with thirty men-at-arms and was subsequently made leader of the army, and knighted.
In 1378 he petitioned King Richard II that he had, at his request, accompanied the Lord Justice, James Butler, 2nd Earl of Ormond "in a certain amount of great hosting" of the O'Morchoes of Slewmargy (Sliabh Mairge), with numerous horsemen in his retinue, whereof six of his men were lost as well as four coats of mail and other armour.
In 1379 he was sent to England a second time to report on the state of Irish affairs, accompanied by the soldier and statesman Sir John Cruys of Thorncastle.
He was, with Sir Philip Courtenay, the Lord Justice, active in imposing law and order in Leinster and Merthyr and elsewhere, and in resisting rebels all at his own expense.