Hampton knew of the existence of the ford and, late on 25 October, he decided to send 1,500 men of his first brigade (including most, if not all, of his light infantry) under Colonel Robert Purdy, to cross to the south bank of the Chateauguay, circle round the British position and outflank it by capturing the ford at dawn, while the remainder under Brigadier General George Izard attacked from the front. After Purdy set off, Hampton received a letter from Armstrong, dated 16 October, informing him that Armstrong himself was relinquishing overall command of the combined American forces, leaving Wilkinson in charge. Hampton was also ordered to construct winter quarters for 10,000 men on the Saint Lawrence. Hampton interpreted this instruction to mean that there would be no attack on Montreal that year and the entire campaign was pointless. He would probably have retreated immediately, except that Purdy would then have been left isolated.