Montgomery ordered a new battery constructed closer to the walls and Lamb selected a site some 700yds (640m) from the Porte St Jean, behind some houses. With the earth frozen digging was out of the question, so the gunners filled their gabions with snow and doused them with water to create walls of ice. The battery was finished in three nights and was soon the target of British fire, but the results were not visible as the houses were in the way. Carleton ordered them demolished, but his gunners set them ablaze instead and a strong wind almost carried the fire into the city. A few days later, he refused demands from his officers to burn St Foy and St Roche.
However, with the houses gone, Lamb's battery was exposed and quickly destroyed - two guns were knocked out, three men killed and several others wounded. On the night of 17 December, the guns were removed, and the following day Montgomery made one last effort to coax Carleton into surrendering. Arnold delivered a letter promising Carleton and Cramahe safe passage to England, but was kept waiting outside the gates until one of Carleton's aides announced from the walls that the governor would neither read the letter nor treat with rebels.
Montgomery was now being urged to storm the city without further delay (although rumors that he already had were sweeping England and North America). His Canadians wanted action and the enlistments of many American soldiers would expire on 31 December. He wrote to David Wooster and George Washington, oudining the difficulties and promising to attack at the first heavy snowstorm, relying on the garrison being spread thinly around the city whilst concentrating his own forces. On Christmas Day, he told the army of his plan. Most of the troops supported it and he received a rousing cheer, heard on the ramparts, but a significant number admitted to being apprehensive or downright skeptical. On 27 December, a snowstorm blew up, lasting all day and into the night. The troops made ready - the New Yorkers and four musket companies from Arnold's contingent would attack the Cape Diamond Bastion, whilst Greene would lead the rest into the Lower Town. However, just after midnight the wind died, the sky cleared, and the attack was cancelled - fortuitously as it turned out, as a prisoner and a deserter had escaped and warned Carleton. Montgomery changed his plan, but now had another problem to deal with - smallpox. A second hospital was established three miles (5km) away, but it was soon overflowing and, despite orders to the contrary, many men inoculated themselves.
On the afternoon of 30 December, another storm blew up. By nightfall it had become the heavy "northeaster" Montgomery desired and around 4.00am he ordered the troops to form up. He would lead 300 New Yorkers past Cape Diamond and into the Lower Town from the south. Arnold, with 600 men including 50 gunners, would leave St Roche and attack from the north through the Sault au Matelot. At the same time Livingston would feint against the Porte St Jean with his Canadians, and Brown would engage the Cape Diamond bastion with 100 men. Montgomery and Arnold would join forces and head into the Upper Town, hoping the merchants would panic and force Carleton to surrender. In fact, Carleton had issued orders to burn the wharves and warehouses in such an event.
