Union of Moldovia and Wallachia! is a unique decision, which forms the country of 
Romania. It is an alternative to the traditional Form Romania decision.
It is available to 
Moldavia and 
Wallachia. It requires that both nations are not puppets and have invented State and Government. (They both start as puppets of The 
Ottoman Empire). Romania must also not exist.
When one of the two countries take the decision, it will change the country to Romania and give 10 prestige. It will also move the capital to Bucharest (ID 664).
The other nation will then get an event, where they can join the Union. Moldovia gets the event Wallachian Winds and Wallachia gets the event Moldovian Winds.
The player has to watch out, if one tries to enact this decision. It is not likely that only one of the two nations can enact the decision while the other one is not able to so. Only very early in the game where, State and Government might not be invented by both sides. So it will become a race to press the button.