Intermarium (, ) was a post-World War I geopolitical plan conceived by Józef Piłsudski to unite former Polish–Lithuanian Commonwealth lands within a single polity. The plan went through several iterations, some of which anticipated the inclusion as well of other, neighboring states. The proposed multinational polity would have incorporated territories lying between the Baltic, Black and Adriatic Seas, hence the name Intermarium (Latin for "Between-Seas"). Prospectively a federation of Central and Eastern European countries, the post-World War I Intermarium plan pursued by Piłsudski sought to recruit to the proposed federation the Baltic states (Lithuania, Latvia, Estonia), Finland, Belarus, Ukraine, Hungary, Romania, Yugoslavia and Czechoslovakia. The Polish name Międzymorze (from między, "between"; and morze, "sea"), meaning "Between-Seas", was rendered into Latin as Intermarium. The proposed federation was meant to emulate the Polish–Lithuanian Commonwealth, stretching from the Baltic Sea to the Black Sea, that, from the end of the 16th century to the end of the 18th, had united the Kingdom of Poland and the Grand Duchy of Lithuania. Intermarium complemented Piłsudski's other geopolitical vision, Prometheism, whose goal was the dismemberment of the Russian Empire and that Empire's divestment of its territorial acquisitions. Intermarium was perceived by some Lithuanians as a threat to their newly established independence, and by some Ukrainians as a threat to their aspirations for independence, and while France backed the proposal, it was opposed by the Soviet Union and by most other Western powers. Within two decades of the failure of Piłsudski's grand scheme, all the countries that he had viewed as candidates for membership in the Intermarium federation had fallen to the Soviet Union or to Nazi Germany, except for Finland (which suffered some territorial losses in the 1939–40 Winter War with the Soviet Union). Precedents Commonwealth A Polish–Lithuanian union and military alliance had come about as a mutual response to common threats posed by the Teutonic Order, the Golden Horde and the Grand Duchy of Moscow. The alliance was first established in 1385 by the Union of Krewo, solemnized by the marriage of Poland's Queen Jadwiga and Lithuania's Grand Duke Jogaila of the Gediminid dynasty, who became King Władysław II Jagiełło of Poland. A longer-lasting federation subsequently came about in 1569 in the form of the Polish–Lithuanian Commonwealth, an arrangement that lasted until 1795, i.e., until the Third Partition of the Polish–Lithuanian Commonwealth. The Polish–Lithuanian alliance thus lasted a total of 410 years, and constituted at