On May 31, 1813, Brigadier-General Vincent and his troops abandoned Fort George and began to retreat toward Burlington Heights, the strip of land on which Dundurn Castle in Hamilton stands. The situation was critical because the capital, York, had been bombarded by the American fleet under Commodore Chauncey and the chief officials had abandoned the town. Now an American force twice the size of the British had taken Fort George and was marching after Vincent. Lieutenant Crowther of the 49th Regiment was sent out with a scouting party to discover the position of the Americans. His small force found the Americans near Red Hill Creek and, after a brief skirmish, reported back to his commander, Lt. Col. John Harvey.

Harvey wanted more information so the intrepid Lt. James FitzGibbon volunteered to try a bit of spying. Dressed as a settler, FitzGibbon entered the American camp selling butter. His Irish blarney worked so well that, not only did he manage to examine the complete camp and determine the size and composition of the American force, but he also managed to sell all the butter at a good price. On receiving FitzGibbon's report, Harvey felt sure that a night attack was called for.

Meanwhile, a settler named Isaac Corman had been caught by the Americans. On being interrogated, he found that his interrogator was a second cousin from Kentucky. The cousin decided to let him go, at which point Corman asked how he was going to get out of the camp because he didn't know the password. To his astonishment, the American told him that it was "wilhenhar", the first three letters of each name of William Henry Harrison. Corman then left. He met his brother-in-law, Billy Green, told him what had happened and gave him the password. Green then jumped on a horse and rode to Col. Harvey.

This information convinced Harvey that the British must attack. He managed to convince General Vincent and, at 3 a.m. on June 6, the British attacked. With a little more luck, they might have destroyed the Americans but a sentry managed to fire a shot and this alerted the Americans. Still, the attack was so successful that the British captured the American guns and two American generals, Chandler and Winder. The Americans panicked and fled from the scene. Harvey, not wishing to reveal that his force was much weaker than the American, withdrew before daylight. The American force retreated to Forty Mile Creek (Grimsby) and the threat to York and Burlington Heights was over for the time being.

The battle had other consequences. FitzGibbon was encouraged by the success of his spying and suggested to Harvey that, with a small group of men, he could conduct hit-and-run operations against the Americans and counter the attacks that were being made by American groups led by Chapin and Willcocks. With Ensign Winder and forty-eight hand-picked Irishmen, his small detachment of the 49th became the famous Green 'Uns, whose exploits caused a response from the Americans that led to the Battle of Beaver Dams.