The division of the command in the Confederate army had been productive of most disastrous consequences.  The rivalry between O’Neill, Preston, and Owen Roe, increased the complication; but the Nuncio managed to reconcile the two O’Neills, and active preparations were made by Owen Roe for his famous northern campaign.  The Irish troops intended for Charles had remained in their own country; the unfortunate monarch had committed his last fatal error by confiding himself to his Scotch subjects, who sold him to his own people for L400,000.  Ormonde now refused to publish the treaty which had been just concluded, or even to enforce its observance by Monroe, although the Confederates had given him L3,000 to get up an expedition for that purpose.

In the beginning of June, A.D. 1646, Owen Roe O’Neill marched against Monroe, with 5,000 foot and 500 horse.  Monroe received notice of his approach; and although his force was far superior to O’Neill’s, he sent for reinforcements of cavalry from his brother, Colonel George Monroe, who was stationed at Coleraine.  But the Irish forces advanced more quickly than he expected; and on the 4th of June they had crossed the Blackwater, and encamped at Benburb.  O’Neill selected his position admirably.  He encamped between two small hills, with a wood in his rear.  The river Blackwater protected him on the right, and an impassable bog on the left.  Some brushwood in the front enabled him to conceal a party of musketeers; he was also well-informed of Monroe’s movements, and took precautions to prevent the advance of his brother’s forces.  Monroe crossed the river at Kinard, at a considerable distance in the rear of his opponent, and then advanced, by a circuitous march, from the east and north.  The approach was anticipated; and, on in the 5th of June, 1646, the most magnificent victory ever recorded in the annals of Irish history was won.  The Irish army prepared for the great day with solemn religious observances.  The whole army approached the sacraments of penance and holy communion, and thus were prepared alike for death or victory.  The chaplain deputed by the Nuncio addressed them briefly, and appealed to their religious feelings; their General, Owen Roe, appealed to their nationality.  How deeply outraged they had been, both in their religion and in their national feelings, has been already mentioned; how they fought for their altars and their domestic hearths will now be recorded.  O’Neill’s skill as a military tactician, is beyond all praise.  For four long hours he engaged the attention of the enemy, until the glare of the burning summer sun had passed away, and until he had intercepted the reinforcements which Monroe expected.  At last the decisive moment had arrived.  Monroe thought he saw his brother’s contingent in the distance; O’Neill knew that they were some of his own men who had beaten that very contingent.  When the Scotch general was undeceived, he resolved to retire.  O’Neill saw his advantage, and gave the command to charge.