Seven Years' War (1756–63), a power struggle in Europe, North America, and India that involved most of the nations of Europe. Prussia emerged from the war as a powerful state. Great Britain, victorious over France, became the world's greatest colonial power.
Maria Theresa, ruler of Austria, resolved to check the rising power of Frederick II of Prussia. During the War of the Austrian Succession (1740–48) he had taken Silesia, a rich province, from her. To regain it, she formed against Frederick a very powerful coalition that included Austria, Russia, France, Saxony, and Sweden.
Great Britain signed a treaty with Frederick early in 1756. This treaty in effect loosely allied the two countries against their common enemy, France, and any other nation that might attack the German state of Hanover, which was ruled by George II, the British monarch.
Frederick invaded Saxony in 1756 and Bohemia in 1757. He was allied with four small German states, including Hanover. Frederick, with British financial aid, was victorious at first. In 1759 he suffered a major defeat by the Austrians and Russians at Kunersdorf, in Brandenburg. Prussia was reduced to fighting defensive battles for the remainder of the war. Meanwhile, in the Mediterranean, the French had taken Minorca from Britain. France began to prepare an invasion of England, but was thwarted when the British fleet blockaded French ports. In the fall of 1759 the British defeated the French decisively at Lagos Bay and at Quiberon Bay.
In 1762 Spain entered the conflict in support of France and joined in an attack on Portugal, which had refused to close its ports to British ships. Britain helped to repulse the attack. Busy with France and Spain, Britain could give little aid to Prussia, and Frederick seemed on the brink of defeat. He was saved by three unrelated events. Sweden failed in an attempt to conquer Pomerania and withdrew from the war. Peter III succeeded to the Russian throne and quickly made peace with Frederick, whom he had long admired. Then France, whose military resources were being exhausted fighting Britain in the colonies, deserted the Austrian cause. Austria then agreed to make peace with Prussia.
The American phase of the war is called the French and Indian War. It started in 1754 when the British set out to expel the French from the Ohio Valley, where French forts were being built to link together Canada and Louisiana. Although unsuccessful at first, the British finally defeated the French both in what is now the United States and in Canada. The decisive event was the capture of Quebec in 1759.
Britain and France competed for the rich Indian trade by supporting rival native puppet rulers. Robert Clive, in the service of the British East India Company, captured a French center at Chandernagor and gained control of Bengal at the battle of Plassey in 1757. The major French center of Pondichery fell to the British in 1761.
Austria and Prussia signed a treaty at Hubertusburg, in Saxony, in 1763. Prussia kept Silesia, and other boundaries were uncharged. Prussia had established itself as an important European power. By the Treaty of Paris in the same year, Great Britain was given France's mainland possessions in North America; Chandernagor and Pondichéry were returned to France, on condition they not be used for military purposes. And Spain, in exchange for the return of Havana and Manila, which had been taken in the war, ceded Florida to Great Britain. In a separate treaty, France gave Spain, its ally, territory west of the Mississippi.