Ireland entered into a continuous state of war with the rebellion of 1641, with most of the island controlled by the Irish Confederates. Increasingly threatened by the armies of the English Parliament after Charles I's arrest in 1648, the Confederates signed a treaty of alliance with the English Royalists. The joint Royalist and Confederate forces under the Duke of Ormonde attempted to eliminate the Parliamentary army holding Dublin, but their opponents routed them at the Battle of Rathmines (2 August 1649). As the former Member of Parliament Admiral Robert Blake blockaded Prince Rupert's fleet in Kinsale, Oliver Cromwell could land at Dublin on 15 August 1649 with an army to quell the Royalist alliance in Ireland.