Brian O'Neill was born to the House of O'Neill of County Donegal. Born in Lifford, Brian O'Neill was a powerful leader who sought not only to advance his clan, but also the Irish cause. He fought against the English as a young man and commanded armies for his family until he became High King in 1258.
King Brian's first steps in the rebellion were to liberate the Province of Ulster by capturing Derry from the English in the north, while his isolated nobles in the south took over territory from the Anglo-Irish. However, the English sent more forces to Ireland to crush the Irish rebellion, which was gaining ground. King Brian's worst defeat was the Battle of Druim Dearg in 1260, during which he was slain alongside several other Gaelic chiefs. His death in battle led to the quelling of the uprising.