On April 19, 1775, 700 British soldiers marched from Boston to forestall a rebellion of the colonists by capturing a colonial arms depot in the nearby town of Concord. At the village of Lexington, they confronted 70 militiamen. Someone - no one knows who - fired a shot, and the American War of Independence began. The British easily captured Lexington and Concord, but as they marched back to Boston they were harassed by hundreds of Massachusetts volunteers. By June, 10,000 American soldiers had besieged Boston, and the British were forced to evacuate the city in March 1776.
In May 1775, a second Continental Congress had met in Philadelphia and began to assume the functions of a national government. It founded a Continental Army and Navy under the command of George Washington, a Virginia planter and veteran of the French and Indian War. It printed paper money and opened diplomatic relations with foreign powers. On July 2, 1776, the Congress finally resolved "That these United Colonies are, and of right ought to be free and independent states." Thomas Jefferson of Virginia, assisted by others, drafted a Declaration of Independence, which the Congress adopted on July 4, 1776.
The Declaration presented a public defense of the American Revolution, including a lengthy list of grievances against the British king, George III. Most importantly, it explained the philosophy behind the revolution - that men have a natural right to "Life, Liberty and the pursuit of Happiness"; that governments can rule only with "the consent of the governed"; that any government may be dissolved when it fails to protect the rights of the people. This theory of politics came from the British philosopher John Locke, and it is central to the Anglo-Saxon political tradition.
Early in 1776 the British government decided to use overwhelming military force to crush the American revolt. The task looked easy. England, Wales, and Scotland had a combined population of about 9 million, compared with 2.5 million in the 13 rebel colonies, nearly 20 percent of whom were black slaves. Militarily, Britain was clearly superior, with a large standing army and the financial resources to hire additional troops, and the most powerful navy in the world. The British government also counted on mobilizing thousands of Loyalists in America and Native Americans who were hostile to white expansion.
Nonetheless, the Americans had a number of important advantages. They were fighting on their own territory, close to the sources of supply and amid a mostly friendly population. In addition, the Patriots had some resourceful military leaders, who had been tested in the French and Indian War. Finally, later in the war, the rebellious colonies received crucial aid from France and Spain. This assistance offset British superiority in wealth and military power, and made possible a clear-cut American victory. However, few of these American advantages were obvious when the war began.
At first, the war went badly for the Americans. The British captured New York City in September 1776, and Philadelphia was captured a year later. The tide turned in October 1777, when a British army under General John Burgoyne surrendered at Saratoga, in northern New York. Encouraged by that victory, France seized an opportunity to humble Britain, her traditional enemy. A Franco-American alliance was signed in February 1778. With few provisions and little training, American troops generally fought well, but they might have lost the war if they had not received aid from the French treasury and the powerful French Navy.
After 1778, the fighting shifted largely to the south. In 1781, 8,000 British troops under General George Cornwallis were surrounded at Yorktown, Virginia, by a French fleet and a combined French-American army under George Washington's command. Cornwallis surrendered, and soon afterward the British government asked for peace. The Treaty of Paris, signed in September 1783, recognized the independence of the United States and granted the new nation all the territory north of Florida, south of Canada and east of the Mississippi River.