The crisis point of the Elizabethan conquest of Ireland came when the English authorities tried to extend their authority over Ulster and Aodh Mór Ó Néill, the most powerful Irish lord in Ireland. Though initially appearing to support the crown, Ó Néill engaged in a proxy war in Fermanagh and northern Connacht, by sending troops to aid Aodh Mag Uidhir lord of Fermanagh. This distracted the crown with military campaigns in the west while Tyrone consolidated his power in Ulster. Ó Néill openly broke with the crown in February 1595 when his forces took and destroyed the Blackwater Fort on the Armagh-Tyrone border. Later named the Nine Years War, Ó Néill focused his action in Ulster and along its borders, until Spanish promises of aid in 1596 led him to spread the conflict to the rest of Ireland. What was a war for regional autonomy had become one for the control of Ireland. The Irish victory at the Battle of the Yellow Ford, the collapse of the Munster Plantation, followed by the dismal vice-royalty of Robert Devereux, 2nd Earl of Essex brought the power of the crown in Ireland to the point of collapse.