some consolidation of European territories used to be provided by dynastic unions; less common were country-level unions, such as the Polish–Lithuanian Commonwealth and Austro-Hungarian Empire. In the Congress of Aix-la-Chapelle of 1818, Tsar Alexander, as the most advanced internationalist of the day, suggested a kind of permanent European union and even proposed the maintenance of international military forces to provide recognised states with support against changes by violence. Pan-European political thought truly emerged during the 19th century, inspired by the liberal ideas of the French and American Revolutions. The following Napoleonic Wars and First French Empire (1804–1815), brought down the Holy Roman Empire, enabled nationalism and following the Congress of Vienna, the ideals of internationalism like with Immanuel Kant and European unity flourished across the continent, especially in the writings of Wojciech Jastrzębowski (1799–1882) or Giuseppe Mazzini (1805–1872). The term United States of Europe () was used at that time by Victor Hugo (1802–1885) during a speech at the International Peace Congress held in Paris in 1849: From World War I to World War II During the interwar period, the consciousness that national markets in Europe were interdependent though confrontational, along with the observation of a larger and growing US market on the other side of the ocean, nourished the urge for the economic integration of the continent. In 1920, advocating the creation of a European economic union, the British economist John Maynard Keynes wrote that "a Free Trade Union should be established ... to impose no protectionist tariffs whatever against the produce of other members of the Union." During the same decade, the Austrian Richard von Coudenhove-Kalergi, in light of the dissolution of the Habsburg Empire, imaginrd as one of the first a modern political union of Europe and founded the Pan-Europa Movement. His ideas influenced his contemporaries, among whom was then-Prime Minister of France Aristide Briand. In 1929, the latter gave a speech in favour of a European Union before the assembly of the League of Nations, the precursor of the United Nations. World War II (1939-1945) World War II from 1939 to 1945 demonstrated more than ever the horrors of war, but particularly also of extremism, of discrimination and of genocide. As with devastating wars before, there was a desire to ensure it could never happen again, particularly with the war bringing the world nuclear weapons. Most European countries failed to maintain their Great Power status, with