Though he was known as a brave and bold officer, his campaigning experience was limited to minor affairs in the West Indies. In spite of this, the 38 year-old Riall was to be second in-command of Lt. Gen. Gordon Drummond's forces in the volatile Niagara region.
Riall and Drummond went on the offensive late that same year, recapturing Fort George from the Americans in December and took the American fort of Niagara as well. In retaliation for the American burning campaign that began in Newark, Riall devastated Lewiston and the Tuscarora village before recrossing to Canada.
In the last days of 1813, Riall continued these retaliatory measures by burning Buffalo and nearby Black Rock. He was in Fort George the following summer when the Americans invaded Canada at Fort Erie. Two days later, he moved his forces north of the Chippawa River in an attempt to counter the advancing Americans. He underestimated both the numbers and capabilities of Brig. Gen. Winfield Scott's men, and did not call for available reinforcements. His army had to retreat from the Americans on the battlefield at Chippawa and fortunately, had a well-protected position to withdraw to.
Riall eventually returned his men to Fort George to regroup and plan another foray against the Americans. With Maj. Gen. Gordon Drummond on his way from York to take command, Riall took no chances calling on both the militia and reserves from Burlington Heights. It was this force that he brought forward again to meet the Americans and was attacked by Scott's army at Lundy's Lane. Initially, he ordered a retreat when Drummond arrived with his troops but the battle was already engaged. Riall was severely wounded in the arm early on in the battle, and was being transported to the rear when his party was captured by an advanced American unit. After the battle, he was evacuated to Buffalo where his arm had to be amputated.
Ironically, Riall spent weeks convalescing in the same room as the injured Scott. For both men, the war was over. Due to his uncommonly high rank, it wasn't until December that he was exchanged back to Canada.
Riall returned to England after peace was concluded and was subsequently appointed governor of Grenada. He remained active in the military and rose to the rank of lieutenant general.
He died in 1850