Polish–Czechoslovak confederation
The Polish–Czechoslovak confederation, or Polish–Czechoslovak federation, was a political concept from the time of World War II, supported by the Polish government-in-exile and, to a lesser extent, the United Kingdom and the United States. It was a revitalisation of the Intermarium concept, proposing the creation of a federation based on Poland and Czechoslovakia.
Source: Wikipedia — Polish–Czechoslovak confederation (CC BY-SA 4.0)