“We Shall Be Undone”
In the Fall of 1775, the Americans launched an invasion of Canada. The defending British forces were concentrated in the western part of the province, especially at Fort Saint-Jean. In the eastern part of the province, Lieutenant-Colonel Allan Maclean safeguarded Quebec, a strategically valuable city and the seat of government.
Unbeknownst to the British, the American invasion was made in two parts. General Richard Montgomery led the main effort in the west. In the east, Colonel Benedict Arnold led a secretive expedition through the wilderness of Maine and southern Canada in a bid to take the city of surprise. His march was a remarkable achievement, and one of the most celebrated events of the war.
Arnold’s expedition was nearly successful as British attention was focused elsewhere. At the time Arnold reached the St. Lawrence River, the city of Quebec was defended by only a handful of regulars. Maclean, and most of his men had moved west to Sorel. Meanwhile, a number of English merchants in Quebec scarcely hid their hopes that the Americans would take over. However, word of Arnold’s expedition leaked out, and the British removed all small craft from the south shore of the river. This stymied Arnold just long enough. By the time the Americans were across the St. Lawrence, Maclean and his men were back in the garrison. 
At this point, the city of Quebec was not in imminent danger, but its fall looked inevitable. Maclean lamented:
“…we have been now ten days invested so that we can get nothing into the Town, and our provisions are by no means Adequate to Maintain the Number of Inhabitants, and if we turn out some thousands, we run a very great risk of having the Canadian Militia Mutiny… But what above all gives me the greatest uneasiness is, that the very best Train of Artillery in Canada fell into the hands of the Rebells at St. John's, there is not a single piece of Brass Ordnance in the Whole Province that they have not got, and if they have got a ship that lay at Montreal with 2000 Barrells of Powder, which I am afraid is the case, we shall be undone…”
Fortunately for the British, the supply of gunpowder had been thrown into the St. Lawrence.
Also, the American army was on the point of dissolution.
“Patience and Perseverance”
Brigadier-General Richard Montgomery’s men had spent a miserable campaign in the swampy forestland around Fort Saint-Jean, during which time much of the army was debilitated by illness. Now the Canadian winter was at hand, and the men were without adequate clothing. Provisions were chronically in short supply and the army was essentially bankrupt. It didn’t help either that most of the Americans’ terms of enlistment were set to expire on December 31st, and the men longed to be with their families again.
Montgomery issued a proclamation at Montreal on November 15 in which he made “acknowledgment to the troops for their patience and perseverance during the course of a fatiguing campaign.” Rather than force dispirited men to campaign with him any longer, he offered “Passess, together with boats and provisions… for such as choose to return home…” However, he asked “the troops not to lay him under the necessity of abandoning Canada; of undoing in one day what has been the work of months,” and he hoped “that none will leave him at this critical juncture but such whose affairs or health absolutely require their return home…”
Montgomery also asked the men to extend their enlistments until April 15th, by which time new regiments could be raised in the colonies and sent into Canada. By way of enticement, he wrote: “Those who engage in this honorable cause shall be furnished completely with every article of clothing requisite for the rigor of the climate, blanket-coats, coats, waistcoat and breeches, one pair of stockings, two shirts, leggins, sacks, shoes, mittens, and a cap, at the Continental charge, and one dollar bounty.”
The response was disappointing. The Green Mountain Boys chose to return home, so too did Bedel’s Rangers, and most of the troops from Connecticut. At least many in Montgomery’s own New York regiments agreed to stick it out. Major John Brown also remained along with many of his men, and James Livingston retained a corps of Canadian troops (soon to be reorganized as the 1st Canadian Regiment).
Another unit that had planned on departing was Lamb’s artillery company. Cannoneer Robert Barwick recorded in his journal on November 18, “our Capt [John Lamb] Came up to know the minds of our Company about [en]Listing but there was scarce one of them that would consent to it, as they been so long from home and wanted to go Back.” 
Lamb’s men, however, seem to have been given the option to leave only after the other unwilling men were dismissed. Lamb’s men then “were told what Difficulty it was in getting down the Lakes in the winter[, and] they began to think it would be best to [en]list again…” Once the other units departed, the Americans suffered from a shortage of bateaux -- the one practical means of returning to New York.
Therefore, Barwick, in spite of his wishes, “went forwards to Quebec although I had but about 4 or 5 weeks to serve of my old inlistment.” Most of the company followed suit.
Montgomery then began to send the troops downriver aboard the vessels captured at Sorel.
“To Die with a Hero”
Lieutenant John Copp of the 1st New York Regiment left Montreal on December 1st and reached Quebec on the 6th. He wrote the following day, “We met herewith Colonel Arnold and his Detachment from Cambridge, he has about 600 men who have suffered innumerable hardships on their March hither. He is really a brave Man, and will no doubt, if his Life is spared, do honor to the American Arms. Great part of the Army left us when they were most wanted, but I flatter myself we shall be able to do without them. The more Danger, the more Glory. If Quebec is taken all is Ours…” 
But Copp admitted that the situation was hardly promising: “the place appears to be almost impregnable… This Evening our Bombardment is to go on, and the Artillery to begin their Attack in different places. Our Chief difficulty is in erecting Batteries, on account of the Frost having hardened the Ground too much for throwing it up.”
The same mix of optimism and fatalism appears in a letter written the same day by an officer stationed at Fort Saint-Jean (now an American depot):
“Heaven seems still to smile upon us… This is the time of the year when in common the rivers about here are froze up, but we have this day calm moderate weather, with a fair wind to carry down the boats with the powder… Gen. Montgomery landed at Point aux Trembles last Friday the 1st inst. on Saturday part of his Army marched for Quebec and he was to follow with the remainder the next day; This we call great news, & if it is true that fortune favours the brave, success must attend our General, for a braver man does not tread on America nor on English leather; to die with such a man is to die with a Hero indeed.” 
1. Maclean left Sorel for other reasons and learned of Arnold's arrival on the St. Lawrence while returning to Quebec.
2. Barwick's journal appears in the series, Naval Documents of the Revolutionary War.
4. Source. The last passage is of course remarkably prescient. I got the chills when reading it.