Roman Catholic Irish were subdued to ethnic cleansing policy by Oliver Cromwell. After his suppression of a rebellion against the English in 1649 he ordered that the Irish were allowed to live west of the Shannon river only. During guerrilla warfare that followed thousands of Irish died or were sold as slaves to America. Cromwell had promised Irish land to the business investors and soldiers who had helped him perform his expeditions. The 'Act for the Attainder of the Rebels in Ireland' of 17 September 1656 is part of this programme. The land of rebels is attained and 'rebels' are defined in such a way that all Catholics match. By the end of 1656 four fifths of the Irish land was in protestant hands.