During the American Revolution, French support became essential to American independence after the 1778 Treaty of Alliance, secured through the efforts of Ben Franklin and others, brought the Continental Army the backing of a powerful French army and navy. Under the Comte de Rochambeau, the French Army marched from Rhode Island intending to join George Washington in an attack on New York City, but after reconnaissance the allied armies instead moved against the British at Yorktown, Virginia, in the final great battle of the war. In 1781 the Hudson River was the only effective north-south crossing and became the place where the American and French armies met and marched toward victory. The French Army encamped twice on and around what is now French Hill in Yorktown, first on August 21, 1781, when Rochambeau's forces camped near Hunt's Tavern and established headquarters there before marching on August 22 from Crompond to Verplank and crossing the Hudson at King's Ferry on the way to Yorktown, and again on their return in 1782, when they camped from September 23 until October 21. During that later stay, the Soissonnais troops camped from French Hill southwest to the power lines, making French Hill and Crompond their longest encampment on the return march. The four French line regiments that landed with Rochambeau and marched south to fight in Virginia, the Regiment de Saintoge, Regiment de Royal Deaux Ponts, Regiment de Bourbonnais, and Regiment de Soissonnais, all encamped in the surrounding area, with attached artillery companies. While in Crompond, the French Army changed the course of the stream for Hallocks Mill to improve the water supply, creating a mill race still visible near Route 202. On October 21, 1782, the French broke camp and marched out of Crompond, and their aid was indispensable to defeating the British and securing the independence of the United States of America.