Intermarium (Polish: Międzymorze) was a geopolitical project conceived by politicians in successor states of the former Polish–Lithuanian Commonwealth in several iterations, some of which anticipated the inclusion as well of other, neighboring states. The proposed multinational polity would have extended across territories lying between the Baltic, Black and Adriatic Seas, hence the name meaning “Between-Seas”.
Intermarium was, however, 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 Russia 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 Nazi Germany, except for Finland (which suffered some territorial losses in the 1939–40 Winter War with the Soviet Union).
The concept of a “Central [and Eastern] European Union”, a triangular geopolitical entity anchored in the Baltic, Black, and Adriatic or Aegean Seas, was revived during World War II in Władysław Sikorski‘s Polish Government in Exile. A first step toward its implementation, 1942 discussions between the Greek, Yugoslav, Polish and Czechoslovak governments in exile regarding prospective Greek-Yugoslav and Polish-Czechoslovak federations, ultimately foundered on Soviet opposition, which led to Czech hesitation and Allied indifference or hostility. A declaration by the Polish Underground State in that period called for the creation of a Central and Eastern European federal union undominated by any one state.
On 12 May 2011, the Visegrád Group countries (Poland, Czech Republic, Slovakia, and Hungary) announced the formation of a Visegrád Battlegroup under Poland’s command. The battlegroup was in place by 2016 as an independent force, not part of the NATO command. In addition, starting in 2013, the four countries were to begin joint military exercises under the auspices of the NATO Response Force. Some scholars saw this as a first step toward close Central European regional cooperation.
On 6 August 2015, Polish PresidentAndrzej Duda, in his inaugural address, announced plans to build a regional alliance of Central European states, modeled on the Intermarium concept. In 2016 the Three Seas Initiative held an initial summit meeting in Dubrovnik, Croatia. The Three Seas Initiative has 12 member states along a north–south axis from the Baltic Sea to the Adriatic Sea and the Black Sea: Estonia, Latvia, Lithuania, Poland, Czech Republic, Slovakia, Austria, Hungary, Slovenia, Croatia, Romania, Bulgaria.
