In 1813, Mallory joined the Canadian Volunteers, a militia formed by Willcocks which fought for the American side during the War of 1812. When Willcocks died during the Siege of Fort Erie in 1814, Mallory was given command of this unit. Mallory was convicted of treason in absentia and his lands in Upper Canada reverted to the Crown.
Battle of Lewiston
On 19 December, the British stormed Fort Niagara and launched a raid into New York under Major General Phineas Riall. In the Battle of Lewiston, Canadian Volunteers under Major Benajah Mallory conducted a fighting retreat for two days, contesting every inch of ground as they fell back to the Tonawanda Creek, where they set fire to the bridge over the unfordable creek to halt the British pursuit. Eight of the Canadian Volunteers were killed.[1][2]