In 1740, King Frederick II (Frederick the Great) came to the throne. Using the pretext of a 1537 treaty (vetoed by Emperor Ferdinand I), by which parts of Silesia were to pass to Brandenburg after the extinction of its ruling Piast dynasty, Frederick invaded Silesia, thereby beginning the War of the Austrian Succession (1740–48). In 1744, Frederick invaded again to forestall reprisals and to claim, this time, the province of Bohemia. He failed, but French pressure on Austria's ally Great Britain led to a series of treaties and compromises, culminating in the 1748 Treaty of Aix-la-Chapelle that restored peace and left Prussia in possession of most of Silesia. When Frederick preemptively invaded Saxony and Bohemia over the course of a few months in 1756–57, he initiated the Seven Years' War. This war was a desperate struggle for the Prussian Army, and the fact that it managed to fight much of Europe to a draw bears witness to Frederick's military skills. The situation became progressively grimmer until the death of Empress Elizabeth of Russia (the miracle of the House of Brandenburg). The accession of the Prussophile Peter III relieved the pressure on the eastern front. Defeating the Austrian army at the Battle of Burkersdorf and relying on continuing British success against France in the war's colonial theatres, Prussia was finally able to force a "status quo ante bellum" on the continent. This result confirmed Prussia's major role within the German states and established the country as a European great power. This gave the start to the rivalry between Prussia and Austria for the leadership of Germany, referred to as German dualism.