King George III Sends His Ambassador to Negotiate a Treaty with Tsar Alexander I of Russia, Which Would Effectively Create Europe's Third Coalition Against Napoleon: This Treaty led to a great battle just months later, the first battle of the War of the Third Coalition, at Austerlitz

The Treaty of Saint Petersburg was signed on April 11, 1805 by Great Britain and the Russian Empire and created an offensive alliance directed against Napoleon's French Empire. The two allies were joined by Austria in August and by Sweden in October. This struck fear into Napoleon and drove conflict during the War of the Third Coalition. The stated goal of the Anglo-Russian alliance was to reduce France to its 1792 borders.

This treaty itself was one of the main causes of the War of the Third Coalition, and paradoxically marked one of the high water marks for Napoleon. After this Treaty, just months later, Austria and Russia suffered a major defeat at Austerlitz. In December 1805, after Austrian defeat at Ulm in addition to Austerlitz, France and Austria signed the Treaty of Pressburg, which took Austria out of the Third Coalition and the war. Thus the first battles of the War of the Third Coalition resulted in great victories for the French.

Document signed, King George III, Court at St. James, January 8, 1805, confirming the appointment of ""Full power to... Granville Leveson Gower our Ambassador Extraordinary to our good brother the Emperor of all the Russias,"" and authorizing him to ""accede to any treaty or treaties which shall be concluded between us and our aforesaid good brother, the Emperor of all the Russias..."" Attached is the full authorization in Latin.