the underbelly of Dublin, within twenty five miles of the city, was necessary. An offensive into the province of Munster was expected, and before he might engage on that campaign Grey had to deal with the O'Byrnes to prevent them attacking him in the rear as he marched south. The campaign resulted in the Battle of Glenmalure. Battle of Glenmalure In 1580, Grey led his army westward through the Pale, ignoring certain veterans who implored him to delay the campaign. He planned to enter Glenmalure from the neighbouring Glen of Imaal and attack O'Byrne's stronghold; the enemy was expected to be flushed from its fastness, whereupon the English cavalry would ride them down in their flight. O'Byrne had remained in the Liffey valley with Baltinglas, but at the approach of the crown army he withdrew into Glenmalure. Grey altered his course and travelled several miles south, where he was joined by Kildare, before heading east in a loop and making an arduous ascent into the mountains. After a row amongst his chief officers, Grey sent an expedition of half his force in royal livery with their colours aloft. The rebel lookout on the peak of Lugnaquilla sounded the alarm, and Grey ordered his men to descend into the glen with a drum roll. O'Byrne had concealed his men in the craggy terrain, and the English troops, conspicuous in their red and blue coats and white hose, instantly found themselves sliding along a river course. Decimated by sniping gunfire, they hit bottom fully a mile in depth from the point where the glen was entered. The Irish did not wait: shots were fired from both sides, and the kern descended to engage in hand-to-hand combat. Grey's troops were routed with the loss of hundreds, and much valuable equipment had to be discarded. Grey spurred his cavalry on to check the pursuit and force the rebels back into the glen, but even on the retreat to Dublin the punishment was withering. Despite this disturbing setback, Grey was in a position to post a garrison in the locality, in the hope that this would contain O'Byrne; but the raids kept coming, even into the suburbs of Dublin. In the campaign that ensued, O'Byrne did suffer losses and failed to dislodge the garrison, but he held out, even after the crown had asserted its command in Munster with the massacre at Smerwick of the