While Cromwell was apparently trying to negotiate surrender terms, some of his soldiers broke into the town, killed 2,000 Irish troops and up to 1,500 civilians, and burned much of the town. After the taking of Drogheda, Cromwell sent a column north to Ulster to secure the north of the country and went on to besiege Waterford, Kilkenny and Clonmel in Ireland's south-east. Kilkenny surrendered on terms, as did many other towns like New Ross and Carlow, but Cromwell failed to take Waterford, and at the siege of Clonmel in May 1650 he lost up to 2,000 men in abortive assaults before the town surrendered. One of his major victories in Ireland was diplomatic rather than military. With the help of Roger Boyle, 1st Earl of Orrery, Cromwell persuaded the Protestant Royalist troops in Cork to change sides and fight with the Parliament. At this point, word reached Cromwell that Charles II (son of Charles I) had landed in Scotland from exile in France and been proclaimed King by the Covenanter regime. Cromwell therefore returned to England from Youghal on 26 May 1650 to counter this threat. The Parliamentarian conquest of Ireland dragged on for almost three years after Cromwell's departure. The campaigns under Cromwell's successors Henry Ireton and Edmund Ludlow mostly consisted of long sieges of fortified cities and guerrilla warfare in the countryside. The last Catholic-held town, Galway, surrendered in April 1652 and the last Irish Catholic troops capitulated in April of the following year. In the wake of the Commonwealth's conquest of the island of Ireland, the public practice of Roman Catholicism was banned and Catholic priests were killed when captured. All Catholic-owned land was confiscated under the Act for the Settlement of Ireland of 1652 and given to Scottish and English settlers, Parliament's financial creditors and Parliamentary soldiers. The remaining Catholic landowners were allocated poorer land in the province of Connacht. The extent of Cromwell's brutality in Ireland has been strongly debated. Some historians argue that Cromwell never accepted that he was responsible for the killing of civilians in Ireland, claiming that he had acted harshly but only against those "in arms". Other historians, however, cite Cromwell's contemporary reports to London including that of 27 September 1649 in which he lists the slaying of 3,000 military personnel, followed by the phrase "and many inhabitants". In September 1649, he justified his sacking of Drogheda as revenge for the massacres of Protestant settlers in Ulster in 1641, calling the massacre "the righteous judgement of God on these barbarous wretches, who have imbrued their hands with so much innocent blood".