Izard had already predicted that the withdrawal of his forces from Plattsburg would leave northeastern New York at the mercy of the British and he spoke the truth. No sooner had his divisions started westward than the British army, ten thousand strong, under General Prevost, crossed the frontier and marched rapidly toward the Saranac River and then straight on to Plattsburg. Possession of this trading town the British particularly desired because through it passed an enormous amount of illicit traffic with Canada. Both Izard and Prevost agreed in the statement that the British army was almost entirely fed on supplies drawn from New York and Vermont by way of Lake Champlain. "Two thirds of the army in Canada are supplied with beef by American contractors," wrote Prevost, and there were not enough highways to accommodate the herds of cattle which were driven across the border. To protect this source of supply by conquering the region was the task assigned the splendid army of British regulars who had fought under Wellington. The conclusion of the Peninsular campaign had released them for service in America, and England was now able for the first time to throw her military strength against the feeble forces of the United States. It was announced as the intention of the British Government to take and hold the lakes, from Champlain to Erie, as territorial waters and a permanent barrier. To oppose the large and seasoned army which was to effect these projects, there was an American force of only fifteen hundred men, led by Brigadier General Alexander Macomb. All he could do was to try to hold the defensive works at Plattsburg and to send forward small skirmishing parties to annoy the British army which advanced in solid column, without taking the trouble to deploy. On the 6th of September Sir George Prevost with his army reached Plattsburg and encamped just outside the town. From a ridge the British leader beheld the redoubts, strong field works, and blockhouses, and at anchor in the bay the little American fleet of Commodore Thomas Macdonough. To Prevost it looked like a costly business to attempt to carry these defenses by assault and he therefore decided to await the arrival of the British ships of Captain George Downie. A combined attack by land and sea, he believed, should find no difficulty in wiping out American resistance.