Born in North Carolina, Forsyth joined the United States Army in 1800 as an officer and was a captain of the Regiment of Riflemen at the outbreak of war in 1812.
He led raids into Upper Canada along the Saint Lawrence River in 1812–13 before transferring south and taking part in the battles of York and Fort George.
[2] Based at Ogdensburg, New York, during the autumn and winter of 1812, he led the successful Raid on Gananoque and other attacks across the Saint Lawrence River, which threatened the British supply lines to their forces in Upper Canada.
[3] Forsyth sent Bennet C. Riley with about a half dozen riflemen upriver to gather firewood in a boat.
Benjamin Forsyth and his riflemen rowed out on their boat providing sniper covering fire for Riley's crew.
The British gunboats were held at bay as Riley and Forsyth both withdrew safely back to their fort in their boats.
[4] The Raid on Elizabethtown occurred on February 7, 1813, when Benjamin Forsyth and 200 men crossed the frozen St. Lawrence River to occupy Elizabethtown and seize military and public stores, free American prisoners, then capture British military prisoners.
[2] On February 22, 1813, the British used a temporary superiority in strength to drive Forsyth from his positions at the Battle of Ogdensburg.
The riflemen in the fort held out against the frontal attack, mainly because the British guns became stuck in snow drifts, and American artillery, under Adjutant Daniel W. Church of Colonel Benedict's regiment and Lieutenant Baird of Forsyth's company, fired on the British with mixed results.
American militia who had been dislodged from their position fell back while conducting a harassing fire by shooting at the British from behind houses and trees.
The British burned the boats and schooners frozen into the ice, and they carried off artillery and military stores.
[8] Forsyth's company was ordered to join the main American force at Sackett's Harbor rather than reoccupy Ogdensburg.
While a group of Seneca and American militiamen on horses led by Cyrenius Chapin would lure the Mohawks to the ambush site by conducting a feigned retreat.
The hidden American riflemen and Seneca gunners rose out of their concealment and opened a heavy fire on the Mohawks.
Riley, Forsyth, and their riflemen were performing paramilitary operations in British Canada in support of America's invasion.
The ruse seemed so convincing that the teenaged boys told Forsyth of valuable intelligence about a blockhouse that was being built to contest the American advance.
[14] On March 30, 1814, Benjamin Forsyth, Bennet C. Riley, and their riflemen spearheaded an attack on British-allied forces who were retreating back to a blockhouse.
[17] Later in the year on June 24, 1814, Forsyth and his men took part in the campaign aimed at capturing Montreal, but were not present at the Battle of Crysler's Farm.
Forsyth commanded Riley to tell the rest of the riflemen to casually withdraw so as not to cause the Indians and Canadians to be eager to launch their ambush.
All 70 American riflemen opened a simultaneous volley fire killing or wounding a number of Canadians and Indians.
On 28 June 1814, Forsyth, commanding the Regiment of Riflemen, advanced from Chazy, New York, to Odelltown, intending to draw a Canadian-Indian into an ambush.
[19][20] When the Canadian-Indian force responded, the American decoys conducted a feigned retreat, which successfully lured 150 Canadians and Indian allies into the ambush site.
[19][20] During the ensuing fight, Forsyth needlessly exposed himself by stepping on a log to watch the attack and was shot and killed.
[19][20] Forsyth's riflemen, still hidden and now enraged over the death of their commander, rose from their covered positions and fired a devastating volley.
[19][20] Even though Forsyth was killed, his feigned retreat and ambush succeeded at inflicting heavy casualties on the Canadian-Indian force.