After returning from Egypt, Napoleon engineered a coup in November 1799 and became First Consul of the Republic. Another victory over the Austrians at the Battle of Marengo in 1800 secured his political power. With the Concordat of 1801, Napoleon restored the religious privileges of the Catholic Church while keeping the lands seized by the Revolution. The state continued to nominate the bishops and to control church finances. He extended his political control over France until the Senate declared him Emperor of the French in 1804, launching the French Empire. Intractable differences with the British meant that the French were facing a Third Coalition by 1805. Napoleon shattered this coalition with decisive victories in the Ulm Campaign and a historic triumph at the Battle of Austerlitz, which led to the elimination of the Holy Roman Empire. In October 1805, however, a Franco-Spanish fleet was destroyed at the Battle of Trafalgar, allowing Britain to impose a naval blockade of the French coasts. In retaliation, Napoleon established the Continental System in 1806 to cut off continental trade with Britain. The Fourth Coalition took up arms against him the same year because Prussia became worried about growing French influence on the continent. Napoleon knocked out Prussia at the battles of Jena and Auerstedt, then turned his attention towards the Russians and annihilated them in June 1807 at Friedland, which forced the Russians to accept the Treaties of Tilsit.