In foreign policy, tsar Alexander I changed Russia's position relative to France four times between 1804 and 1812 among neutrality, opposition, and alliance. In 1805 he joined Britain in the War of the Third Coalition against Napoleon. After the massive defeat of the Russian and Austrian armies by Napoleon at the Battle of Austerlitz in 1805, Russian official propaganda blamed the Austrians and stressed the moral superiority of tsar Alexander I. He switched sides and formed an alliance with Napoleon by the Treaty of Tilsit (1807) and joined Napoleon's Continental System of economic boycotts against Britain. He and Napoleon could never agree, especially about Poland, and the alliance collapsed by 1810. The tsar's greatest triumph came in 1812 as Napoleon's invasion of Russia proved a total disaster for the French. The initiative swung toward the Allies. Russian armies joined the others in pushing the French all the way back, seizing Paris, and forcing Napoleon to abdicate in 1814.