Since the moment we launched the assault—and in its aftermath—we have learned many things we didn’t know at the time were already working against us.

First, the storm we needed to conceal our movement was also a warning to Gov. Carleton and his second in command, Allan Maclean. As the snow started, Maclean predicted, “The rebels will come tonight.” Hours before Capt. Brown fired the five flares, the garrison was preparing for us.

The British knew our artillery was unable to breach their west walls, so they left them lightly defended and positioned most of their garrison to the north and south sides of the city in anticipation of the very kind of double envelopment attack we have planned. So, when Captain Brown and Colonel Livingston launched their feints at Diamond Bastion and St. John’s Gate, the intended distractions were totally ineffective.

We might still have succeeded, had General Montgomery’s attack from the south prevailed. His long column was first held up just past Cape Diamond by two rows of heavy abatis that took far longer for the pioneers to chop through than expected.

At 7:00 a.m., the general and a handful of his men finally made their way through a narrow gap hacked through the abatis. But then—despite heavy, blowing snow—they see a fortified house about fifty yards ahead with apertures for muskets and cannons.

No smoke or sound issued from the place, no sign of footprints in the snow—getting deeper by the minute. The general assembled a handful of his officers and men, and a dozen or so slowly crept forward—a forlorn hope led by a general officer.

Unbeknownst to Montgomery and his New Yorkers, there were thirty armed British and Canadian militiamen and a handful of Royal Navy sailors with four light artillery pieces loaded with grapeshot inside. These inexperienced British defenders silently watched until Montgomery and his advance party were less than twenty yards away. Only then did the militia captain inside the structure yell, “Fire!”

The devastating salvo of grapeshot and musket balls immediately killed General Montgomery, three other officers, and nine New York soldiers. The next field grade officer to come upon the gruesome scene was Lieutenant Colonel Campbell, the division’s quartermaster who was not equipped for battlefield leadership.

Within minutes of the carnage, Campbell ordered a retreat. Diminutive Aaron Burr more than a foot shorter than the general tried to carry his commander off the field but collapsed under the general’s weight and was forced to withdraw. It was from Mr. Burr I got this account.

Col. Arnold and his northern attackers were totally unaware of the catastrophe that just occurred a half mile to their south.

Arnold’s column initially moved slowly and unobserved from St. Roche but soon came under heavy musket fire from the city walls to their right.