On the following morning, to the great joy of the besieged, the Surprise frigate and a sloop arrived in the harbor, with one hundred seventy men of the Twenty-ninth regiment and some marines, who were speedily landed. Now General Carleton at once resolved on offensive operations, and marched out at noon with one thousand men and a few field-pieces to attack the Americans. But the latter did not await his approach, and fled with the utmost precipitation, leaving all their cannon, stores, ammunition, and even their sick behind. These were treated with the utmost attention by General Carleton, whose humanity won the esteem of all his prisoners, who were loud in his praise on returning home. For his services during the siege the Governor was knighted by his sovereign.
The Americans retreated as rapidly as possible for a distance of forty-five miles up the river, but finding they were not pursued they halted for a few days to rest themselves. They then proceeded in a distressed condition to Sorel, where they were joined by some reënforcements, and where, also, their general, Thomas, died of the smallpox, which still continued to afflict them. He was succeeded in the chief command by General Sullivan.
Meantime some companies of the Eighth regiment, which were scattered through the frontier posts on the Lakes, had descended to Ogdensburg. From thence Captain Forster was detached, on May 11th, with one hundred twenty-six soldiers and an equal number of Indians, to capture a stockade at the Cedars, garrisoned by three hundred ninety Americans, under the command of Colonel Bedell. The latter surrendered on the 19th, after sustaining only a few hours' fire of musketry, and the following day one hundred men advancing to his assistance were attacked by the Indians and a few Canadians. A smart action ensued which lasted for ten minutes, when the Americans laid down their arms and were marched prisoners to the fort, where they were with difficulty saved from massacre.
After providing for the safety of his numerous prisoners, Forster pushed down the river toward Lachine, but, learning that Arnold was advancing to attack him with a force treble his own number, he halted and prepared for action. Placing his men in an advantageous position on the edge of the river, and spreading the Indians out on his flanks, he made such a stout defence that the Americans were compelled to retire to St. Anne's. Forster, encumbered with his prisoners, now proposed a cartel, which Arnold at once assented to, and an exchange was effected, on May 27th, for two majors, nine captains, twenty subalterns, and four hundred forty-three privates. This cartel was broken by Congress, on the ground that the prisoners had been cruelly used, which was not the case. They had been treated with all the humanity possible, when the difficulty of guarding so large a number, with less than three hundred men, is taken into consideration.
While these events were in progress above Montreal, a large body of troops had arrived from England, under the command of Major-General Burgoyne. Brigadier Fraser was at once sent on by the Governor with the first division to Three Rivers. While the troops still remained on board their transports off this place, General Thompson advanced with eighteen hundred men to surprise the town, and would have effected his object had not one of his Canadian guides escaped and warned the British of his approach. General Fraser immediately landed his troops, with several field-pieces, and posted them so advantageously that the Americans were speedily defeated, their general, his second in command, and five hundred men made prisoners, while, the retreat of their main body being cut off, they were compelled to take shelter in a wood full of swamps. Here they remained in great distress till the following day, when General Carleton, who had meanwhile come up, humanely drew the guard from the bridge over the Rivière du Loup, and allowed them to escape toward Sorel. Finding themselves unable to oppose the force advancing against them, the American army, under Sullivan, retreated to Crown Point, whither Arnold also retired from Montreal on June 15th. Thus terminated the invasion of Canada, which produced no advantage to the American cause, but on the contrary aroused the hostility of the inhabitants and drew them closer to Great Britain.