The British hastily enforced a naval blockade of France to starve it of resources. Napoleon responded with economic embargoes against Britain, and sought to eliminate Britain's Continental allies to break the coalitions arrayed against him. The so-called "Continental System" formed a league of armed neutrality to disrupt the blockade and enforce free trade with France. The British responded by capturing the Danish fleet, breaking up the league, and later secured dominance over the seas, allowing it to freely continue its strategy. But Napoleon won the War of the Third Coalition at Austerlitz, forcing the Austrian Empire out of the war and formally dissolving the Holy Roman Empire. Within months, Prussia declared war, triggering a War of the Fourth Coalition. This war ended disastrously for Prussia, defeated and occupied within 19 days of the beginning of the campaign. Napoleon subsequently defeated Russia at Friedland, creating powerful client states in Eastern Europe and ending the fourth coalition.