Ethan Allen, a prominent leader of the Green Mountain Boys, initiated an ambitious plan to capture Montreal, believing that the city would be a significant blow to British authority in Canada during the early stages of the American Revolutionary War. On September 25, Allen and his troops approached Longue-Pointe, close to Montreal. The goal was to surprise and dislodge the British garrison, which was critical to maintaining British dominance in the region. Allen's expedition was driven by the notion that seizing Montreal could rally support for the colonial cause and inspire further resistance against British rule.

However, the attack did not go as planned. The British forces were well-prepared and outmatched Allen's troops, who faced numerous logistic challenges and a lack of sufficient reinforcements. In the confrontation at Longue-Pointe, Allen's forces found themselves overwhelmed and ultimately had to surrender to the British. This defeat was particularly significant as it showcased the difficulties faced by American forces when conducting operations in enemy territory, especially against a well-organized British military.

The surrender at Longue-Pointe highlighted the need for better coordination among the American forces and underscored the British resolve to maintain control over Canada. Allen's capture was a temporary setback, but it did not diminish the ongoing revolutionary fervor in the American colonies. In the broader context of the war, this event signified the challenges of early military ventures and the strategic complications associated with expanding the conflict into Canada, influencing future planning of military engagements by American leaders as the war progressed.