Initially O'Neill assisted the English, hoping to be named as Lord President of Ulster himself. Elizabeth I, though, had feared that O'Neill had no intention of being a simple landlord and that his ambition was to usurp her authority and be "a Prince of Ulster". For this reason she refused to grant O'Neill provincial presidency or any other position which would have given him authority to govern Ulster on the crown's behalf. Once it became clear that Henry Bagenal was marked to assume the presidency of Ulster, O'Neill accepted that an English offensive was inevitable, and so joined his allies in open rebellion in February 1595, with an assault on the Blackwater Fort, which guarded a strategic bridge on the River Blackwater.