The first and most pressing reason was an alliance signed in 1649 between the Irish Confederate Catholics, Charles II, proclaimed King of Ireland in January 1649, and the English Royalists. This allowed for Royalist troops to be sent to Ireland and put the Irish Confederate Catholic troops under the command of Royalist officers led by James Butler, Earl of Ormonde. Their aim was to invade England and restore the monarchy there. This was a threat which the new English Commonwealth could not afford to ignore.