The War of the Austrian Succession (1740–48) had left Austria humiliated. Seeking to recover Silesia from Prussia, Empress Maria Theresa even before the conclusion of that war had secured the alliance of Elizabeth of Russia. In the years following the Treaty of Aix-la-Chapelle (1748), Kaunitz, as Austrian ambassador to France and then as chancellor, worked for a rapprochement with France.

In 1755, when hostilities broke out in North America, George II, king of England and elector of Hanover, negotiated the Treaty of Westminster with Frederick II of Prussia, who guaranteed the neutrality of Hanover. This event hastened the alliance (1756) of France and Austria, sometimes called the "diplomatic revolution." Shortly afterward Frederick II opened hostilities by invading Saxony. In Jan., 1757, war was declared on the aggressor in the name of the Holy Roman Empire. Austria concluded alliances with France and Russia and was joined by Sweden. The main European phase of the war began with the Prussian invasion of Bohemia early in 1757.

Victorious at first, Frederick was severely defeated by the Austrians under Daun at Kolin (June, 1757) and had to evacuate Bohemia. The fighting was carried into Saxony and Silesia, where Frederick gained the great victories of Rossbach (Nov., 1757) and Leuthen (Dec., 1757) over the French and Austrians. The Russians, who had invaded Prussia, were defeated by Frederick at Zorndorf (Aug., 1758). The English and Hanoverians, at first unsuccessful against the French in NW Germany, began a vigorous effort when William Pitt (later earl of Chatham) came into power; the troops then won the victories of Krefeld (June, 1758) and Minden (Aug., 1759).

However, Frederick soon found himself in an almost desperate situation. He was badly beaten by Daun at Kunersdorf (Aug., 1759) and in Nov., 1759, Daun captured a Prussian army of 13,000 at Maxen. In Oct., 1760, the Russians took Berlin. Days later, as Frederick's army approached, they evacuated it, and in November Frederick defeated Daun at Torgau. Nonetheless, his situation remained critical, especially after the fall of Pitt (1761) deprived him of British subsidies. The death (Jan., 1762) of Elizabeth of Russia and the accession of Peter III, Frederick's ardent admirer, helped save him from defeat.

By the Treaty of St. Petersburg (1762) Russia made peace and restored all conquests; Sweden made peace in the same year. Now fighting alone in the east, the Austrians were soundly defeated at Burkersdorf (July, 1762). The French, too, had suffered severe reverses. In America they had lost Louisburg (1758), Quebec (1759), and some possessions in the West Indies; in India, the British victories at Plassey (1757) and Pondichéry (now Puducherry; 1761) had destroyed French power; on the sea, the French took Port Mahón from the British (1757) but were defeated by Hawke in Quiberon Bay (1759). The entry of Spain into the war under the terms of the Family Compact of 1761 was of little help to France, where the war had never been popular.

After protracted negotiations between the war-weary powers, peace was made (Feb., 1763) among Prussia, Austria, and Saxony at Hubertusburg, and among England, France, and Spain at Paris (see Paris, Treaty of, 1763). The treaty of Hubertusburg, though it restored the prewar status quo, marked the ascendancy of Prussia as a leading European power. Through the Treaty of Paris, Great Britain emerged as the world's chief colonial empire, which was its primary goal in the war, and France lost most of its overseas possessions. For Russia the Seven Years War was the first great venture into purely European affairs.

See studies by L. J. Oliva (1964), R. Savory (1966), and H. H. Kaplan (1968).