James seems to have hoped that William’s army would be mowed down by disease, as Schomberg’s had been in the preceding campaign.  And there is reason to believe that Tyrconnell, foreseeing the defeat of James, wished to avoid any serious fighting, which would be an obstacle in his way when he sought to patch up a peace with the victor and make terms for himself.  But his opponent was inspired by a very different temper, and William’s army advanced steadily southwards, to find James encamped on the southern bank of the Boyne.

There were several fords by which William’s army would have to cross on its way south.  But James was such an incapable general that he did not even throw up trenches to defend the fords.  William’s army arrived and encamped on the north bank of the river, and the next day, June 30th, was employed in an artillery duel between the two armies, when considerable injury was inflicted on William’s forces, although he was far stronger in artillery than his opponent.  During that night, James, already certain of defeat, sent away most of his artillery to Dublin, leaving only six guns with his army on the Boyne.

It seems tolerably certain that, when the battle began again next day, William’s army numbered between forty-five and fifty thousand, with the usual proportion of cavalry,—­probably a tenth of the whole.  James, on the other hand, had from twenty to twenty-five thousand men, about a tenth of them, probably, being mounted; he had, by his own fault, only six guns against about fifty in William’s batteries.  William’s line of battle was formed, as usual, with the infantry in the center and the cavalry on the wings.  He gave the elder Schomberg command of the center, while Schomberg’s son, with the cavalry of the right wing, was sent four or five miles up the river to Slane, to cross there and turn the left flank of the opposing army.  William himself led the cavalry on the left wing, and later on in the battle, descending the river, crossed at a lower ford.  He could thus attack the right flank of his opponent; the infantry composing the center of his army advancing, meanwhile, under cover of a heavy artillery fire, and forcing the fords of the Boyne.

The river is shallow here, and in the middle of summer the water is nowhere too deep for wading, so that it was a very slight protection to the army of James.  A better general would at least have chosen a stronger position, and one which would have given him some manifest advantage.  Such positions were to be found all along the road by which William had advanced from Carrickfergus.  The country on both sides of the Boyne is flat; rolling meadows with the shallow river dividing them—­a country giving every opportunity to cavalry.

William’s right, under the younger Schomberg, made several unsuccessful attempts to cross the river at Slane, being repeatedly beaten back by Arthur O’Neill’s horse.  Finally, however, the way was cleared for him by a vigorous cannonade, to which O’Neill, having no cannon, was unable to reply, and William’s right wing thus forced the passage of the Boyne.