In the summer of 1642, the Scottish Parliament sent some 10,000 soldiers to quell the Irish rebellion. In revenge for the massacres of Scottish colonists, the army committed many atrocities against the Catholic population. Based in Carrickfergus, the Scottish army fought against the rebels until 1650. In the northwest of Ulster, the colonists around Derry and east Donegal organised the Laggan Army in self-defence. The British forces fought an inconclusive war with the Ulster Irish led by Owen Roe O'Neill. All sides committed atrocities against civilians in this war, exacerbating the population displacement begun by the Plantation.