On April 12, 1808, following the Chesapeake–Leopard affair, the U.S. Congress passed legislation authorizing an increase in the size of the U.S. Army, to include a regiment of riflemen.

On April 12, 1812, two companies of the regiment under the command of then Lieutenant Colonel Thomas A. Smith occupied Fort Mose, Spanish East Florida as part of the Patriot War.

Smith attempted a siege of St. Augustine, Florida, but his supply lines were not secure and the Spanish garrison of Castillo de San Marcos threatened his command.

Benjamin Forsyth and his riflemen rowed out on their boat providing sniper covering fire for Riley's crew.

[9] In October 1812, two companies of riflemen were assigned to participate in the Battle of Queenston Heights; however disagreement between Major General Stephen Van Rensselaer and Brigadier General Alexander Smyth resulted in those companies being withdrawn because Smyth thought it more important that they clean their camp following a storm.

[8]: 42 Alexander Smyth who was a commander of the Regiment of Riflemen orchestrated and ordered a raid on the British that would take place on November 28, 1812.

Smyth instructed the regulars and sailors to spike the British artillery guns and destroy a bridge in preparation for an invasion of Canada.

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.

[2]: 31–33 [8]: 53 Forsyth's company was ordered to join the main American force at Sackett's Harbor rather than reoccupy Ogdensburg.

Despite that the American commander Pike who was killed in this raid explicitly instructed his soldiers not to conduct any looting or burning private property.

[15][16][2]: 34–35 On May 27, 1813, a battalion of the regiment commanded by Forsyth executed another amphibious assault and participated in the capture of Fort George, Upper Canada.

After taking the fort, US troops attempted to pursue the retreating British forces but Major General Morgan Lewis recalled the battalion when he feared an ambush.

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 teenage boys told Forsyth all valuable intelligence about a blockhouse that was being built to contest the American advance.

Wade Hampton ordered American colonel Isaac Clarke to undertake a “petty war” at the border between Vermont and Lower Canada to stifle smuggling and to divert British attention from his force.On October 12, 1813.

Issac Clarke with about 102 riflemen crossed in boats from Chazy, New York, to a point near Philipsburg, Lower Canada, on Missisquoi Bay (the eastern basin in the northern reach of Lake Champlain) and seized the village, which was guarded by a detachment of the 4th battalion of Select Embodied militia of Lower Canada militia.

[2]: 39–40 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.

[25] Riflemen under the command of Major Daniel Appling participated in the Battle of Big Sandy Creek on May 30, 1814, during which they ambushed and captured a large detachment of British sailors, including two Royal Navy captains, and Royal Marines, sparing a shipment of large cannon from capture.

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.

[30][28] During the ensuing fight, Forsyth needlessly exposed himself by stepping on a log to watch the attack and was shot and killed.

[30][28] Forsyth's riflemen, still hidden and now enraged over the death of their commander, rose from their covered positions and fired a devastating volley.

[30][28] On August 3, 1814, another detachment of riflemen under the command of Major Lodowick Morgan ambushed and repelled a British raid at Conjocta Creek near Buffalo, New York, prior to the Siege of Fort Erie.

Major Morgan launched another hit-and-run attack on the British to support a detachment of 80 riflemen under American Captain Birdsall who had been sent to cut off a working party of the enemy, engaged in opening an avenue for a battery through the woods.

In the chaotic attack, the Americans destroyed 3 batteries of cannons, blew up the magazine, and inflicted heavy casualties on the British.

While the larger numerically superior British army was marching, Appling and his riflemen fell back conducting delaying actions.

[40][3][41] The regiment's last wartime action occurred after Britain and the United States agreed to end the war in the Treaty of Ghent.

On January 13, 1815, Royal Marines and troops of the 2nd West India Regiment landed near Fort Peter, Saint Marys, Georgia.

[2]: 69 In 1819, Secretary of War John C. Calhoun ordered the Yellowstone Expedition, commanded by Colonel Henry Atkinson, to act as a warning against British incursions.