An American relief force sent to relieve the siege of Fort Schuyler was ambushed by British and Native Americans at Orinsky. The Americans managed to fight themselves out of the ambush, severly depleting the British forces and opening the way for the later relief of the fort.
The British Northern Campaign called for the convergence of separate forces: Burgonyne's troops coming down via Fort Ticonderoga and Lake Champlain and Colonel St. Leger's troops attempting to envelope the Mohawk valley with 1,000 Native American warriors. St. Leger expected to easily overwhelm the small dilapidated fort, called Fort Stanwich. Since St. Leger believed the fort was garrisoned by only a few Americans.
What St. Leger found at the fort instead was a rebuilt force with 550 Americans, commanded by an energetic Colonel Peter Gansevoort. That group was reinforced, as he arrived, by an additional 200 Massachusetts volunteers. St. Leger demanded the immediate surrender of the fort, a demand that was summarily rejected. St. Leger started to lay siege to the fort. He was, however, not optimistic about his immediate prospects. As the fort was well armed, having more cannons than St. Leger had at his disposal.
Meanwhile, the American Brigadier General, Herkimer was leading a force of over 800 men in a relief expedition to the fort. On August 6, 1777 as the relief force approached, St. Leger sent a force, primarily made up of Native Americans, to ambush the approaching relief column.
Six miles from Fort Stanwich, near the village of Oriskany, the British and Indians attacked as the column was traversing a deep ravine. The Americans were surrounded. However, the soldiers held their ground and fought bravely. Faced with no option but to fight or die, they fought a bitter engagement to a standstill. Each side lost over 150 men that day. The American commander, General Herkimer, was soon to die from his wounds.
All thoughts of relieving the fort were forgotten. St. Leger continued his investment of the fort with renewed vigor after the arrival of his cannons. He once again demanded the surrender of the fort. St. Leger threatened that, if they did not surrender, he and the Native Americans would massacre not only the defenders, but the entire patriot population of the valley. The Americans, once again, refused indignantly. Two men, however, snuck through the enemy lines to appeal for help. Help was indeed coming, in the form of Benedict Arnold leading part of Schuyler's army. Arnold spread the rumors that his 800 men were actually 3,000. That was enough to convince the Native Americans the battle was lost. They revolted and St. Leger had no choice but to withdraw and return to Canada.