Essex departed Dublin on 28 August, and the army was mustered three days later outside Kells, making up 3,700 foot and 300 horse. O'Neill's readiness to outflank him and attack the Pale restrained Essex from advancing further, and in a letter to the Queen (""weary with life"") he explained that Kells should be the frontier garrison for the coming winter. On 2 September he marched to Ardee, where O'Neill was sighted with his army on the far side of the Lagan, ""a mile and a half from our quarter, but a river and a wood between him and us"". The English claimed variously that the rebel leader had 10,000 foot and 1,000 horse, or 5,000 and 700. Heeding counsel not to engage because of the inferiority of his forces, Essex embattled the army and encamped on the left bank of the Lagan. O'Neill marched on the flank, keeping to the woods, while his horse-scouts stayed within sight.