At dawn, a force of 10,000 men, led by Count Meinhard Schomberg and General James Douglas, left the Williamite camp near Tullyallen and marched upstream to attack the Jacobite left wing.
Slane bridge had been broken down by James's troops, and the Williamites forded the river at a point between Rossnaree and Slane which "led to a very fine plain"
A charge by a regiment of Jacobite dragoons (mounted infantry) held up their advance for half-an-hour, until the Jacobite commander, Sir Neil O Neill, was gravely wounded. The movement of Meinhard Schomberg's force seriously alarmed James's high command, who responded by sending 17,000 men upstream form Donore to strengthen the left wing.
The bulk of the Jacobite army then confronted Meinhard Schombarg's troops on the high ground south of the river at Roughgrange.