The almost humorous part of all this was that while the demonstration was going on and the town itself was agog with excitement, the garrison gave no sign, much to Clark's mystification. In truth, none of the French having conveyed the news to Hamilton, he and his soldiers, in blissful ignorance of it, were placidly entertaining themselves in various ways. Secure in what was virtually an island stronghold, moated by leagues of flooded lowlands, the idea of an attack like this was a remote from their minds as a visitation of archangels from the skies. An unwonted stir among the townsmen was noticed, but little attention paid to it, and even when the attack on the fort was actually begun they thought the shooting was by some of the drunken Indians. Clark says their first intimation as to the real situation was when one of their men was shot through a porthole, while an apocryphal story, worth preserving as such, is to the effect that Captain Helm, the American officer, now captive, and some of the British officers were engaged in a friendly game of cards, while a whisky toddy was brewing on the hearth, when a rifle ball striking the chimney top knocked dirt into the drink. Helm instantly guessed at the meaning of the firing and affirmed that General Clark had come and was going to take the fort.

This first firing occurred after dark and continued throughout the night of February 23rd. The excitement of the occasion keyed up the assailants to heroic performance and made the assault, as Captain Bowman expressed it, "fine sport for the Sons of Liberty." They had time to dispose themselves about the fort as they saw fit, and, protected by houses, fences and embankments, where the artillery could not be trained on them, they ruthlessly picked off the artillerymen through the embrasures till few dared stand to their guns. The next morning Clark sent to Hamilton a demand to surrender couched in the rather arrogant language of a certain conqueror; to which Hamilton retorted that he and his garrison were "not disposed to be awed into any action unworthy of British subjects." Meanwhile, the Americans had eaten breakfast, the first full meal they had enjoyed for six days, and now were in fine fettle for some more fighting, which was at once granted them. After another hot fusillade a flag of truce came from Hamilton with a letter proposing an armistice, which Clark refused, acceding to nothing short of the surrender of the garrison as "prisoners at discretion."

Some more fighting and then Hamilton, with one-sixth of his dependable men put out of the conflict, began to seriously consider that, among other things, he was six hundred miles from succor and that honorable terms might be the part of prudence. The result of this was a conference between the tow commanders in which Clark, with characteristic high-handedness, had everything his own way.