Battle of York
Sheaffe succeeded Brock as Upper Canada's military commander and acting Lieutenant Governor. He took the oath of office at York on 20 October 1812, but continued to spend much of his time at Fort George. That winter, he suffered from poor health and was preoccupied with military matters. In February, Sheaffe moved from Fort George to York. He opened the legislature of Upper Canada on 25 February 1813 and prorogued it two weeks later. Several bills were passed during the brief session, including legislation that authorized the creation of an incorporated militia battalion made up of volunteers who enlisted for the duration of the war. Another bill provided annuities for disabled militiamen and for the widows and children of those killed.
On 27 April 1813, a force of 1,700 American regulars led by Brigadier General Zebulon Pike landed a few miles west of York, supported by a fleet of 14 warships commanded by Commodore Isaac Chauncey. Defending York were two companies of the 8th Regiment of Foot, a company of the Royal Newfoundland Regiment of Fencible Infantry, a company of the Glengarry Light Infantry Fencibles, a detachment of the 49th Regiment of Foot, and a Royal Artillery detachment for a total of 413 regulars. Supporting the regulars were 477 militia, mostly from the 1st and 3rd York Regiments, and an estimated 50 Mississauga and Ojibwe warriors under the direction of Major James Givins. Most of the regulars were housed in a stockaded garrison located west of town on the east side of Garrison Creek. Sheaffe's headquarters were at Government House on the creek's west side. Further to the west was the stone-walled "grand magazine" that held about 300 barrels of gunpowder, 750 explosive shells and 40,000 musket rounds. Four artillery batteries protected the entrance to the harbour, including the Western Battery, 700 yards (640 m) west of Government House, which mounted two obsolete 18-pounder long guns. With 18 guns in total, the British batteries were outmatched by the 83 guns mounted on the ships of Chauncey's squadron.
Sheaffe was at Government House when the Americans began landing. He quickly dispatched Givins with the Mississauga and Ojibwe to oppose the landing while the regulars and militia assembled. The Glengarries were ordered to support Givens but, for some inexplicable reason, they followed the militia, which had been sent north to block the road running west from York. The grenadier company of the 8th Foot was sent in their place but was forced back after suffering heavy casualties. Sheaffe then advanced in column with the Royal Newfoundland Fencibles and the second company of the 8th Foot. The British formed a line at a clearing 1,000 yards (910 m) west of Government House. Sheaffe ordered the Fencibles forward. The retreating grenadiers passed through the advancing line, pursued by the Americans who now engaged the Fencibles. The Fencibles fell back under heavy fire but were rallied by Sheaffe. The entire line advanced but was once again repulsed. Sheaffe then ordered a withdrawal back to the Western Battery.
The landing took place out of sight of the batteries, and Chauncey's fleet had remained out of range.
After disembarking their passengers, however, several schooners moved inshore and opened fire on the batteries. The British returned fire, but a gunner at the Western Battery accidentally caused a box of cartridges to explode, killing ten and wounding many others. With casualties mounting, Sheaffe decided that the battle was lost. He withdrew his regulars into York and ordered the magazine destroyed.
Pike waited until the rest of his force had landed, then slowly proceeded forward. He had advanced to within 400 yards (370 m) of Government House and had sent an infantry detachment forward to conduct a reconnaissance when the magazine exploded. Debris flew in a 500-yard (460 m) radius, instantly killing 40 American soldiers. Over 200 were wounded, including Pike, who soon succumbed to his wounds. Despite this, the Americans continued their march towards York. Sheaffe ordered the destruction of the partially built sloop-of-war Sir Isaac Brock, then began a 160 mile (260 km) march east to Kingston. Lieutenant Colonel William Chewett and Major William Allan of the 3rd York Militia were left to negotiate the terms of surrender.
A total of 82 regulars, militia and Indigenous warriors were killed during the defence of York. An additional 111 were wounded, and seven were missing in action. 343 men were taken prisoner of whom 68 were wounded. Sheaffe regulars suffered the most casualties with 71 killed, seven missing, 31 wounded and 57 taken prisoner.
Sheaffe's decision to retreat was denounced by several of York's prominent citizens, spurred by the looting and destruction that took place during the six-day American occupation of York. In a letter to Prevost, written by Reverend John Strachan and signed by several of the town's residents, Sheaffe was accused of being indecisive during the battle, failing to give clear orders, and abandoning the town prematurely.
In June 1813, Prevost had Sheaffe replaced as military commander and acting lieutenant governor. In a letter to Henry Bathurst, the Secretary of State for War and the Colonies, Prevost wrote that Sheaffe had "lost the confidence of the province." Sheaffe was briefly placed in charge of troops in the Montreal District, but on Prevost's recommendation was recalled to Britain. Sheaffe departed Quebec for England in November 1813.