Morrison was born in New York (which was then under British occupation in the final days of the American War of Independence), the son of a senior Commissariat officer.

He joined the British Army as an Ensign in 1793, and was present as a Lieutenant in the Anglo-Russian invasion of Holland in 1799, where he was severely wounded at the Battle of Egmont-op-Zee.

The battalion was stationed in Gibraltar in 1812 when war broke out between Britain and the United States, and it was despatched to reinforce the British troops in Canada.

In October 1813, the 2/89th were stationed at Kingston in Upper Canada when news arrived that a large American force was descending the Saint Lawrence River, intent on attacking Montreal.

Major General James Wilkinson, commanding the American army, determined to drive Morrison's force away before proceeding further down the river.