Fort Stanwix, at the western end of the Mohawk River Valley, was a primary defense point for the Continental Army against the British and indigenous forces aligned against them during the American Revolutionary War.

The besieging force was composed of British regulars, Loyalist soldiers, Hessians, and indigenous warriors, under the command of Brigadier General Barry St. Leger.

St. Leger's expedition was a diversion in support of Lieutenant General John Burgoyne's campaign to take control of the Hudson River Valley to the east.

When the American Revolutionary War widened in 1776 to include the frontier areas between New York and the Province of Quebec, the site again became strategically important.

[4] In March 1777 Germain issued orders assigning the expedition to Lieutenant Colonel Barry St. Leger, an experienced frontier fighter who had served in the French and Indian War.

[5][6] In April 1777, Continental Army Major General Philip Schuyler ordered the 3rd New York Regiment under the command of Colonel Peter Gansevoort to occupy and rehabilitate Fort Stanwix as a defense against British and indigenous incursions from Quebec.

He expected these to be adequate for the taking of a dilapidated fort with about 60 defenders, which was the latest intelligence he had when the expedition left Lachine, near Montreal, on June 26.

[6][12] St. Leger first learned that the Americans had occupied Fort Stanwix in force when prisoners captured from its garrison were brought to him on the St. Lawrence River.

[13] He learned from the prisoners that the fort had been repaired and was "garrisoned by upwards of 600 men" and that "the rebels are expecting us, and are acquainted with our strength and route".

[14] Daniel Claus, a British Indian Department superintendent accompanying the expedition, convinced St. Leger to proceed to Oswego on Lake Ontario rather than ascend the Salmon River as originally planned.

They arrived at Oswego on July 25, where about 100 British Indian Department rangers from Fort Niagara led by deputy superintendent John Butler joined the expedition.

Shortly after leaving Oswego, a report reached St. Leger that more supplies for the fort were en route via a convoy of bateaux on the Mohawk River.

[20] St. Leger arrived at Fort Stanwix on the evening of August 2 with the regulars from the 8th and 34th regiments, the jägers, and a company of the Royal Yorkers.

The Canadiens, many of the Indian Department rangers, and the rest of the Royal Yorkers were tasked with clearing Wood Creek and the Oneida Carry, which the Americans had blocked with fallen trees.

Earlier, Gansevoort had his men systematically fell trees across the Oneida Carry, creating abatises, and St. Leger needed to clear the path before his artillery could proceed.

The same day, Brant received word from his sister, Molly, who was living at Canajoharie, that an American relief column was marching up the Mohawk Valley.

[25] By late the next day Herkimer's column had arrived within 10 miles (16 km) of Fort Stanwix where they were joined by about 60 Oneida led by Han Yerry Tewahangarahken.

[26] On August 6, at the bloody confrontation near Oriskany Creek, the Tryon militia suffered catastrophic casualties, including Herkimer, who received a serious wound to the leg.

[30] When the indigenous warriors and Royal Yorkers returned from Oriskany they arrived at camps that had been stripped of much, including blankets, kettles and personal belongings.

[35] After making their way through the swampy ground near the fort they continued down the Mohawk Valley, eventually meeting a relief column under the command of Major General Benedict Arnold.

[36] Schuyler received early reports of the action at Oriskany on August 8,[37] and dispatched Ebenezer Learned's 4th Massachusetts Regiment to relieve the besieged fort the next day.

[38] On August 12, even before Willett could reach him, Schuyler held a war council to decide how to deal with the combined threats of St. Leger and Burgoyne, whose large army was at Fort Edward on the Hudson River.

[44][32] Arnold persuaded Hon Yost to return to Fort Stanwix and spread rumors that large numbers of Americans, under the command of the "Dark Eagle", were about to descend on St. Leger's camp.

[2] Arnold, whose force was augmented by the arrival of friendly Indians, advanced about 10 miles (16 km) toward Fort Stanwix on August 23 when a messenger from Gansevoort notified him of St. Leger's departure.

Early the next day, Arnold detached 500 men to pursue St. Leger, whose column was also being taunted and harassed by his formerly supportive Indian allies.

[48] Leaving a garrison at the fort, with smaller outposts along the Mohawk, Arnold then hurried back with about 1,200 men to rejoin the main army.

[53] In an analysis after the surrender, Burgoyne noted that the failure of General William Howe to support him made it possible for Washington to divert resources from the area around New York City to assist both in the relief of Stanwix and at Saratoga.