Seven Years' War
The first war fought on five continents, which handed Britain an empire and left behind the debts that produced the American and French revolutions.
Between 1756 and 1763 Britain, France, Prussia, Austria, Russia, and Spain fought each other in Europe, North America, the Caribbean, West Africa, India, and the Philippines. Winston Churchill later called it the first world war, and the label fits: one conflict, tied together by navies and by government finance, fought on five continents at once. It ended with Britain holding North America and Bengal.
Two separate quarrels merged into it. The first was German. Frederick the Great of Prussia had seized the rich province of Silesia from Austria in 1740, and Maria Theresa spent sixteen years building the coalition to take it back. The second was colonial. British and French settlers and traders were colliding in the Ohio Valley, where a young Virginian officer named George Washington led the ambush that killed a French envoy in 1754.
The alliances that flipped
In 1756 the great powers swapped partners in what contemporaries called the Diplomatic Revolution. France allied with Austria, its enemy for two centuries. Britain allied with Prussia. Russia joined the attack on Prussia. Frederick was left surrounded by three empires with populations many times his own.
He survived by striking first and marching faster than anyone thought possible. His victories at Rossbach and Leuthen in 1757 are still taught in staff colleges. By 1761 his position was close to hopeless, and what saved him was luck: Empress Elizabeth of Russia died in January 1762, and her nephew Peter III, an open admirer of Frederick, pulled Russia straight out of the war.
Britain buys a war
British strategy under William Pitt was simple. Pay Prussia to keep the French army busy in Europe, and use the Royal Navy to take French possessions everywhere else. It worked almost everywhere it was tried. Quebec fell in 1759 after Wolfe landed below the Plains of Abraham, and French Canada went with it. In India, the East India Company's victories at Plassey in 1757 and Wandiwash in 1760 destroyed French influence and left a trading company collecting the taxes of Bengal. Guadeloupe, Martinique, Senegal, Havana, and Manila all fell too.
The Treaty of Paris in 1763 gave Britain Canada and everything east of the Mississippi. France handed Louisiana to Spain as compensation for its losses. Britain gave back Guadeloupe and Martinique, because at the time a sugar island looked more valuable than a continent of forest.
The bill
Victory roughly doubled Britain's national debt, to about £130 million, and the interest ate most of the government's revenue. London decided that colonists who had been defended by British troops should help pay for them, and passed the Stamp Act in 1765. The colonists had just watched the French threat disappear and saw no reason to pay for protection they no longer needed. Twelve years after the Treaty of Paris they were shooting at British soldiers.
France drew the opposite lesson and spent even more. Backing the American rebels from 1778 gave Paris its revenge and ruined its finances, and the crisis that followed forced Louis XVI to call the Estates-General in 1789. The war made Britain the strongest power on earth, and the debts it left behind helped produce both the American and the French revolutions.