The American naval squadron was spotted by British sentries posted at the Scarborough Bluffs on April 26, who alerted the town and its defenders using flag signals and signal guns. The Militia was ordered to assemble, but only 300 of the 1st and 3rd Regiments of the York Militia, and the Incorporated Militia, could be mustered at short notice. Sheaffe expected the Americans to launch a two-pronged attack, with the main American landing to the west of Fort York, and another landing in Scarborough to cut off a potential retreat to Kingston. To counteract this, Sheaffe concentrated most of his regulars, the Native warriors and a small number of militiamen at Fort York, while most of the militia and the companies of the 8th Regiment of Foot positioned themselves at the town's blockhouse.