The British sent invasion armies and used their powerful navy to blockade the coast. George Washington became the American commander, working with Congress and the states to raise armies and neutralize the influence of Loyalists. Claiming the rule of George III of Great Britain was tyrannical and therefore illegitimate, Congress declared independence as a new nation in July 1776, when Thomas Jefferson wrote and the Congress unanimously approved the United States Declaration of Independence. The British lost Boston in 1776, but then captured and held New York City. The British would capture the revolutionary capital at Philadelphia in 1777, but Congress escaped, and the British withdrew a few months later.
After a British army was captured by the American army at Saratoga, the French balanced naval power by entering the war in 1778 as allies of the United States. The British offered the Americans colonial self-government including freedom from taxation for revenue, but after years of war the Congress was committed to sovereignty and independence. A combined American–French force captured a second British army at Yorktown in 1781, effectively ending the war in the United States. A peace treaty in 1783 confirmed the new nation's complete separation from the British Empire, and resulted in the United States taking possession of nearly all the territory east of the Mississippi River.
The American Revolution was the result of a series of social, political, and intellectual transformations in American society, government and ways of thinking. Americans rejected the aristocracies that dominated Europe at the time, championing instead the