The General Assembly continued to exercise sovreign authority at Kilkenny, collecting revenues, maintaining courts of justice in the provinces, and keeping several armies in the field, most effective of which was undoubtedly that of Owen Roe O’Neill.  We find matters still in this condition three years later, in May, 1646, when Monroe and the Scottish forces prepared to inaugurate an offensive campaign from their base at Carrickfergus.  General Robert Monroe had about seven thousand men at Carrickfergus; his brother George had five hundred at Coleraine; while there was a Scottish army at Derry, numbering about two thousand men.  It was decided to converge these three forces on Clones, in Monaghan, and thence to proceed southwards against the government of the General Assembly, then centered at Limerick.  Clones was sixty miles from Derry, and rather more from Coleraine and Carrickfergus, the two other points of departure.

Owen Roe O’Neill was then at Cavan, fourteen miles south of Clones, with five thousand foot and five hundred horse, all “good, hopeful men,” to use his own words.  General Robert Monroe, starting from Carrickfergus, and marching by Lisburn and Armagh, expected to reach Glasslough, some sixteen miles from Clones, on June 5th.  By a forced march from Cavan, Owen Roe O’Neill reached Glasslough a day earlier, and marching along the northern Blackwater, pitched his camp on the north bank of the river.  Here he was directly in the line between the two Monroes, who could only join their forces after dislodging him; and Robert Monroe, who by that time had reached Armagh, saw that it would be necessary to give battle without delay if the much smaller forces from the north were not to be cut off.

Robert Monroe began a movement northwards towards Owen Roe’s position at dawn on June 5th, and presently reached the Blackwater, to find himself face to face with Owen Roe’s army across the river.  The two forces kept parallel with each other for some time, till Robert Monroe finally forded the Blackwater at Caledon, Owen Roe then retiring in the direction of the current, which here flows north.  Owen Roe, in his movement of withdrawal, brought his army through a narrow pass, which he left in charge of one of his best infantry regiments, with orders to hold it only so long as the enemy could be safely harassed, meanwhile carrying his main body back to the hill of Knocknacloy, the position he had chosen from the first for the battle, and to gain which he had up to this time been manoeuvering.

At Knocknacloy he had the center of his army protected by the hill, the right by a marsh, and the left by the river, so that, a flanking movement on Monroe’s part being impossible, the Scottish general was forced to make a frontal attack.  Under cover of the rearguard action at the pass, which caused both delay and confusion to Monroe’s army, Owen Roe formed his men in order of battle.  His first line was of four columns, with considerable spaces between them; his cavalry was on the right and left wings, behind this first line; while three columns more were drawn up some distance farther back, behind the openings in the front line, and forming the reserve.  We should remember that not only was Owen Roe’s army outnumbered by Monroe’s, but also that Owen Roe had no artillery, while Monroe was well supplied with guns.