Chapter I
By September 1775, the American Revolution had been going on for four months. It was localized mostly in the area around Boston, with battles occurring at Lexington, Concord, and Bunker Hill. The only major "battle", if one could call it that, was the seizure of Fort Ticonderoga in May of that year. However, that was about to change.
On September 4, Richard Montgomery launched an invasion of Canada while his superior, Philip Schuyler, was attending a conference with Native Americans. Although he caught up with the invading force after they had crossed the border, he fell ill shortly afterwards, so command was left to General Montgomery.
On September 17th, the American force began a siege of Fort St. John's. Although Ethan Allen was defeated by the British at the battle of Longue-Pointe and captured, the fort fell on November 3 after a failed relief attempt.
Montgomery and his forces proceeded to Montreal, which fell without much resistance on November 13th. The governor of British Canada and the commander of its forces, Sir Guy Carleton, tried to disguise himself as a commoner escape, but was captured before he could do so [1].
After Montreal fell, General Montgomery moved on to Quebec. Although the city was fortified, it was cut off from reinforcements, and its defending force was disorganized. After a short battle on December 31, the defenders of Quebec were defeated, and the city officially surrendered the following day, on January 1, 1776.
With the fall of Quebec, General Montgomery set up a provincial convention. The predominantly French-Canadian population of Quebec mostly treated the Americans as liberators, and almost all of them at least tolerated the American presence. Soon, the Quebecois had sent a delegation to the Continental Congress, led by Christophe Pélissier, an owner of a local ironworks that had served as an advisor to General Montgomery during the invasion.
In addition, Congress authorized reinforcements to arrive in Quebec, in case the British tried to attack the province. However, realizing that they were at a disadvantage, the British troops decided to defend what they had kept in Canada, especially with the American reinforcements.
Back in New England, the Americans would manage to pull off another success. Henry Knox, a bookseller, was sent from Boston to Fort Ticonderoga, where he began an effort to transport artillery captured from the fort to Boston. This effort was a success. After American troops set up the artillery on Dorchester Heights, the bewildered British decided to evacuate Boston on March 17th, exactly six months after the Siege of Fort John's had begun.
A third triumph had been made by the revolutionaries, but this one was by the pen, not by the sword. Thomas Paine's Common Sense was published on January 10, 1776 in Philadelphia, advocating for independence. Soon, the idea began spreading among many Americans, including those at the Continental Congress. And with the victories in Canada and Boston, some began to think that they might just be able to do it.
[1] - This is the POD. IOTL, Carleton managed to escape from Montreal, organize the British forces in Quebec, and kill Montgomery, leading to an American retreat from Canada.