English government in Ulster in the early 1590s has taken the form of a Provincial Presidency, headed by the colonist Sir Henry Bagenal who lives at Newry.
O'Neill had roused the ire of Bagenal in 1591 by eloping with his sister, Mabel, but in 1593 had showed his loyalty to the crown with his military support for his brother-in-law in the defeat of Hugh Maguire at Belleek.
After Mabel's death, O'Neill had gradually fallen into a barely concealed opposition to the crown and sought aid from Spain and Scotland.
The Nine Years War begins with a conflict over English efforts to maintain a string of garrisons along the southern border of Tyrone's territory in Ulster.
The Irish leader promptly besieges the English garrison at Monaghan castle, and Bagenal marches out to its relief on May 25 (June 4 New Style) from Dundalk, via Newry.
His army is made up of seventeen hundred and fifty troops, including some veterans and certain companies newly arrived from the Spanish campaign in Brittany, but there are many recruits in the ranks.
Bagenal's men are predominantly infantry, armed with muskets and pikes; there is also a small number of horsemen raised in the Pale.
The Battle of Clontibret is essentially a two day running fight, as Bagenal's column is ambushed on its way to and from Monaghan town.
It ends in victory for Tyrone, and is the first severe setback suffered by the English during the war.
