A considerable corps, commanded by General Frazer, had reached the Three Rivers, and the main body was on its way from Quebec.

The distance from the Sorel was about fifty miles, and several armed vessels and transports, full of troops, lay about five miles higher up than the Three Rivers, full in the way.[28] [Footnote 28: Annual Register.] General Thompson, who commanded the army after the illness of General Thomas, understanding the party at the Three Rivers to consist of about eight hundred men, partly Canadians, had detached Colonel St.
Clair with between six and seven hundred men, to attack it, if there should be any probability of doing so with advantage.

Colonel St.
Clair advanced to Nicolet, where, believing himself not strong enough for the service on which he had been ordered, he waited for further reinforcements, or additional instructions.

At this time General Sullivan arrived; and, understanding the enemy to be weak at the Three Rivers, orders General Thompson to join Colonel St.Clair at Nicolet, with a reinforcement of nearly fourteen hundred men, to take command of the whole detachment, and to attack the troops lying at the Three Rivers, provided there was a favourable prospect of success.
{June 8.} General Thompson joined Colonel St.Clair at Nicolet, and, believing himself strong enough to perform the service consigned to him, fell down the river by night, and passed to the other side, with the intention of surprising Frazer.

The plan was to attack the village a little before day-break, at the same instant, at each end; whilst two smaller corps were drawn up to cover and support the attack.
[Sidenote: Battle of the Three Rivers.] The troops passed the armed vessels without being perceived, but arrived at Three Rivers about an hour later than had been intended; in consequence of which they were discovered, and the alarm was given at their landing.