The Battle of Moyry Pass was fought during September and October 1600 in counties Armagh and Louth, in the north of Ireland, during the Nine Years' War. It was the first significant engagement of forces following the cessation of arms agreed in the previous year between the Irish leader Hugh O'Neill and the English Crown commander, the Earl of Essex. The battle was fought by the armies of O'Neill and Lord Mountjoy, a follower of the late Earl of Essex. Mountjoy was determined to pierce O'Neill's heartland in central and western Ulster by the Moyry Pass. In the course of a two-week assault the English troops established a garrison near Armagh, taking heavy casualties, and Mountjoy retired with difficulty to Dundalk. Campaign Mountjoy's strategy for putting down O'Neill's rebellion was gradually to constrict his territory in Ulster with a ring of fortified garrisons on the borders. To this end, he had landed seaborne forces at Derry in the north of the province and at Carrickfergus in the east of Ulster. In September 1600, Mountjoy moved north from Dublin and concentrated at Dundalk, in order to mount an expedition further into Ulster and re-establish a garrison at Armagh, which position had been evacuated by the English Crown forces after O'Neill's victory at the Battle of the Yellow Ford in 1598. On 17 September 1600, Mountjoy set out from Dundalk, intending to march to Newry and then on to Armagh. The Moyry Pass (or "Gap of the North") was the sole point of entry to Ulster (much of the terrain being wooded and mountainous), and it had been well fortified by O'Neill with trenches and barricades. There were three lines of trenches, barricaded with earth and stone, and on the flanks the Irish had made further earth and stone works and 'plashed' (twisted) the branches of low-growing trees in order to provide cover for themselves and prevent the English occupying the heights on either side of the Pass. The battle The English reached the pass on 20 September and set up camp just outside, to the south on Faughart Hill. Taking advantage of a misty day on the 25th, an officer named Thomas Williams (who had commanded the Blackwater Fort during the Battle of the Yellow Ford) made a sortie into the pass. After heavy fighting he identified the Irish defence works and returned to the English camp with 12 dead and