Six-hundred U.S. regulars formed the advance guard of Major-General Dearborn's invasion of Lower Canada. This advance guard was under the command of Colonel Zebulon Pike. The Americans crossed the border from the nearby village of Champlain. It was still dark when they surrounded the blockhouse at Lacolle Mills in the early morning of November 20th 1812. Unknown to the American force the blockhouse was undefended as the Canadian garrison had pulled out the night before. A party of American militia that had taken a different route approached the blockhouse and began to fire at Colonel Pike and his regulars. In the early morning twilight what followed was a confused battle. With the two American forces firing at one another. A short time later, Major de Salaberry, commanding the forward Canadian defences of the Eastern Townships arrived at Lacolle Mills with his Canadian Voltigeurs and 300 Caughnawaga Indians. After a short engagement the American advance guard retreated back to Champlain leaving 5 dead and 5 wounded on the field.
Major-General Dearborn waited three days then withdrew his force to Plattsburgh and ordered the troops into winter quarters.
*NOTE* The Vermont and New York militia flatly refused to cross the border into Canada.