During the 1760s and 1770s, relations between the Thirteen Colonies and Britain became increasingly strained, primarily because of resentment of the British Parliament's ability to tax American colonists without their consent. Disagreement turned to violence and in 1775 the American Revolutionary War began. The following year, the colonists United States Declaration of Independence declared the independence of the United States, thus marking a formal secession. For the first few years, the British populace supported the war, but by 1779 France and Spain had entered on the side of the United States and Britain no longer had secure control of the seas. Its army controlled only a handful of coastal cities. The French and Spanish intervention had the effect of turning the American Revolution into a foreign conflict, which meant that the war itself could not be criticised, only the conduct of it.
1780-81 was a low point for Britain. Taxes and deficits were high, government corruption was pervasive, and the war in America was entering its sixth year with no apparent end in sight. The Gordon Riots erupted in London during the spring of 1781, in response to increased concessions to Catholics by Parliament. In October 1781 Lord Cornwallis surrendered his army at Yorktown, Virginia. The Treaty of Paris was signed in 1783, formally terminating the war and recognising the independence of the United States. However, the British continued to maintain forts along the Canadian border until 1796 and the Great Lakes remained militarised until 1815.
During its first 100 years of operation, the focus of the British East India Company had been trade, not the building of an empire in India. Company interests turned from trade to territory during the 18th century as the Mughal Empire declined in power and the British East India Company struggled with its French counterpart, the La Compagnie française des Indes orientales, during the Carnatic Wars of the 1740s and 1750s. The British, led by Robert Clive, defeated the French and their Indian allies in the Battle of Plassey, leaving the Company in control of Bengal and a major military and political power in India. In the following decades it gradually increased the size of the territories under its control, either ruling directly or indirectly via local puppet rulers under the threat of force of the Indian Army, 80% of which was composed of native Indian sepoys.
At the threshold to the 19th century, Britain was challenged again by France under Napoleon, in a struggle that, unlike previous wars, represented a contest of ideologies between the two nations.