The Battle of Newtown (August 29, 1779) was the only major battle of the Sullivan Expedition, an armed offensive led by Major General John Sullivan that was ordered by George Washington to end the threat of the Iroquois who had sided with the British in the American Revolutionary War. Opposing Sullivan's four brigades were 250 Loyalist soldiers from Butler's Rangers, commanded by Major John Butler, and 350 Iroquois and Delaware (Lenape). Butler and Mohawk war leader Joseph Brant did not want to make a stand at Newtown, and instead proposed to harass the enemy on the march, but were overruled by Sayenqueraghta and other Indigenous war leaders. The engagement occurred along a tall hill, now called Sullivan Hill and part of the Newtown Battlefield State Park. The hillside, running southeast to northwest next to the Chemung River, was a mile long at its crest, which rose 600 feet above the road at its base leading into Newtown. The slope of the hill was covered with pine and dense growth of shrub oak. Hoffman Hollow, a marshy area of small hillocks and thick stands of trees, was just to the east of the hill. A small watercourse, called Baldwin Creek, ran through the hollow and emptied into the Chemung River.

On August 26, 1779, Sullivan left Fort Sullivan, where the two columns of his army had converged, with an estimated 3,200 well-armed troops. They marched slowly up the Chemung River with the intention of destroying the towns and crops of the Six Nations in central New York. On the morning of Sunday, August 29, about ten miles upriver from Fort Sullivan, the advance guard, three companies of riflemen formerly with the Provisional Rifle Corps of Colonel Daniel Morgan, drew close to Butler's position. Suspecting an ambush, they halted and scouted the area. They discovered the hidden breastwork and immediately notified Brigadier General Edward Hand. Hand dispatched his light infantry to take up firing positions behind the bank of Baldwin Creek. The defenders made several unsuccessful attempts at luring the Continentals into an ambush. Nearly all of the Continentals' casualties occurred in the attack of Lieutenant Colonel George Reid's 2nd New Hampshire Regiment. Assigned to the extreme left of Poor's assault formation, it climbed where the slope was steepest and lagged considerably behind the rest of the brigade. Joseph Brant led a counterattack of Indians and nearly encircled Reid.