The Battle of the Cedars was a series of military confrontations in the early stages of the American Revolutionary War that occurred during the Continental Army's invasion of Quebec, which began in September 1775. These skirmishes, which involved limited combat, occurred in May 1776 at and around the Cedars, 28 miles west of Montreal, Quebec. American troops were opposed by a small British Army detachment leading a larger force of Iroquois warriors and Canadian militiamen. Brigadier General Benedict Arnold, commanding the American garrison at Montreal, had placed a detachment of his troops at the Cedars in April 1776, after hearing of rumors of British and Indian military preparations to the west of Montreal. The detachment surrendered on May 19 after a confrontation with a combined Anglo-Iroquois force led by Captain George Forster. American reinforcements on their way to the Cedars were also captured after a brief skirmish on May 20. All of the prisoners were eventually released after negotiations between Forster and Arnold, who brought a sizable force into the area. Forster's force landed near the American-occupied fort on May 18, and sent in a demand for surrender. Butterfield countered with a request to withdraw under arms, which Forster refused. The parties exchanged fire. During the course of the exchange, Forster received word that Sherburne had crossed the Ottawa River from the island of Montreal to Quinze-Chênes but, believing the Cedars to have fallen already, had retreated back across the river.

This news caused the besiegers to redouble their efforts the next day. Additional help arrived for the British in the form of about 40 Canadian militiamen under Jean-Baptiste Testard de Montigny; Forster sent them to harass Sherburne. Following his successes, Forster moved his forces, including all of the prisoners, down to Quinze-Chênes, where more Loyalist militia had assembled. Leaving some of the prisoners there, he advanced on May 23 to Fort Senneville, a fortified works on the southwest tip of Montreal Island that was owned by Montigny. In the meantime, Arnold gathered most of the few remaining forces in Montreal, and sent requests to the outposts around the city for additional troops. By May 24, he was entrenched at Lachine, south of the city, and his force had reached 450 men. Forster began to advance on Lachine, but decided to retreat back to Quinze-Chênes when his scouts notified him of Arnold's position. The Americans never held up their side of the prisoner exchange. Formally repudiating the agreement over the protests of George Washington, Congress accused Forster of mistreating American prisoners by turning them over to the Indians. In a breach of etiquette, the letter containing the repudiation was delivered to Lieutenant General John Burgoyne, instead of the British commander-in-chief and governor of the province, Guy Carleton.