The roots of the Irish Rebellion can be found in the political conditions of the preceding half-century. Until the later sixteenth century, England little interest in Ireland but, following England's retreat from the continent, Ireland began to assume greater importance. Both James and Charles pursued 'plantation' policies in which Scottish and English Protestant settlers pushed the native Irish from their lands in great numbers, and bitterness over this policy fuelled much of the anger and violence. Both sides practised atrocities, but when the Scots and the English settlers fled to the mainland, they carried lurid tales of Catholic persecution. With Protestantism already on the back foot during the Thirty Years War, the English response to the Irish rebellion was marked by extreme paranoia and alarm. Rampant tides of anti-Catholicism swirled around major cities such as London. The war in Ireland was brutal and savage. Under the leadership of Owen Roe O'Neill, the Irish united in the Confederation of Kilkenny to demand toleration for Catholics, and political self-determination. James Butler, Earl of Ormond, represented Crown interests, and his forces were reinforced by detachments of Scottish Presbyterians who flocked across the sea to assist their brethren in distress, adding another layer of religious violence. O'Neill and the Confederates avoided full-scale battles, favouring a form of guerrilla warfare instead.