Bucharest Nine
The Bucharest Nine or the Bucharest Format (B9 or B-9; Romanian: Formatul București, Polish: Bukaresztańska Dziewiątka), or NATO's Eastern Flank (ambiguous as of 2025) is an organization founded on 4 November 2015 in Bucharest, Romania, at the initiative of the president of Romania Klaus Iohannis and the president of Poland Andrzej Duda during a bilateral meeting between them. Its members are Bulgaria, the Czech Republic, Estonia, Hungary, Latvia, Lithuania, Poland, Romania and Slovakia.