From Lake Ontario down to the sea the Canadian frontier was never seriously threatened; and the only action of any consequence was fought to the south of Montreal in the early spring. On March 30 the Americans made a last inglorious attempt in this direction. Wilkinson started with four thousand men to follow the line of Lake Champlain and the Richelieu river, the same that was tried by Dearborn in 1812 and by Hampton in 1813. At La Colle, only four miles across the frontier, he attacked Major Handcock's post of two hundred men. The result was like a second Chateauguay. Handcock drew in three hundred reinforcements and two gunboats from Isle-aux-Noix. Wilkinson's advanced guard lost its way overnight. In the morning he lacked the resolution to press on, even with his overwhelming numbers; and so, after a part of his army had executed some disjointed manoeuvres, he withdrew the whole and gave up in despair. From this point of the Canadian frontier to the very end of the five-thousand-mile loop, that is, from Montreal to Mexico, the theatre of operations was directly based upon the sea, where the British Navy was by this time undisputedly supreme. A very few small American men-of-war were still at large, together with a much greater number of privateers. But they had no power whatever even to mitigate the irresistible blockade of the whole coast-line of the United States. American sea-borne commerce simply died away; for no mercantile marine could have any independent life when its trade had to be carried on by a constantly decreasing tonnage; when, too, it could go to sea at all only by furtive evasion, and when it had to take cargo at risks so great that they could not be covered either by insurance or by any attainable profits. The Atlantic being barred by this Great Blockade, and the Pacific being inaccessible, the only practical way left open to American trade was through the British lines by land or sea. Some American seamen shipped in British vessels. Some American ships sailed under British colours. But the chief external American trade was done illicitly, by 'underground,' with the British West Indies and with Canada itself. This was, of course, in direct defiance of the American government, and to the direct detriment of the United States as a nation. It was equally to the direct benefit of the British colonies in general and of Nova Scotia in particular. American harbours had never been so dull. Quebec and Halifax had never been so prosperous. American money was drained away from the warlike South and West and either concentrated in the Northern States--which were opposed to the war--or paid over into British hands.