He returned to Oxford in December with a scheme for raising 10,000 Irish for service in England and 2000 to join Montrose in Scotland, which through the influence of the duchess of Buckingham secured the consent of the king. On 26 January 1645 Antrim was elevated from Earl to Marquess of Antrim. He returned to Kilkenny in February, took the Irish Confederate oath of association, and was made a member of the council and lieutenant-general of the forces of the Catholic confederacy. The confederacy, however, giving him no support in his projects, he threw up his commission, and with Ormond's help despatched about 1600 men under his kinsman Alasdair MacColla in June to Montrose's assistance in Scotland, sparking a Scottish civil war. Antrim subsequently returned to Oxford and was sent by the king in 1645 with letters for the queen at Saint-Germain-en-Laye.