(1775–83) War that won political independence for 13 of Britain's North American colonies, which formed the United States of America. After the end of the costly French and Indian War (1763), Britain imposed new taxes (see Stamp Act; Sugar Act) and trade restrictions on the colonies, fueling growing resentment and strengthening the colonists' objection to their lack of representation in the British Parliament. Determined to achieve independence, the colonies formed the Continental Army, composed chiefly of minutemen, to challenge Britain's large, organized militia. The war began when Britain sent a force to destroy rebel military stores at Concord, Mass. After fighting broke out on April 19, 1775 (see Battles of Lexington and Concord), rebel forces began a siege of Boston that ended when American forces under Henry Knox forced out the British troops under William Howe on March 17, 1776 (see Battle of Bunker Hill). Britain's offer of pardon in exchange for surrender was refused by the Americans, who declared themselves independent on July 4, 1776 (see Declaration of Independence). British forces retaliated by driving the army of George Washington from New York to New Jersey. On December 25, Washington crossed the Delaware River and won the battles of Trenton and Princeton. The British army split to cover more territory, a fatal error. In engaging the Americans in Pennsylvania, notably in the Battle of the Brandywine, they left the troops in the north vulnerable. Despite a victory in the Battle of Ticonderoga, British troops under John Burgoyne were defeated by Horatio Gates and Benedict Arnold in the Battle of Saratoga (Oct. 17, 1777). Washington quartered his 11,000 troops through a bleak winter at Valley Forge, where they received training from Frederick Steuben that gave them victory in Monmouth, N.J., on June 28, 1778. British forces in the north thenceforth chiefly concentrated near New York. France, which had been secretly furnishing aid to the Americans since 1776, finally declared war on Britain in June 1778. French troops assisted American troops in the south, culminating in the successful Siege of Yorktown, where Charles Cornwallis surrendered his forces on Oct. 19, 1781, bringing an end to the war on land. War continued at sea, fought chiefly between Britain and the U.S.'s European allies. The navies of Spain and the Netherlands contained most of Britain's navy near Europe and away from the fighting in America. The last battle of the war was won by the American navy under John Barry in March 1783 in the Straits of Florida. With the Treaty of Paris (Sept. 3, 1783), Britain recognized the independence of the U.S. east of the Mississippi River and ceded Florida to Spain.