The Bucharest Nine: Enhancing Security on NATO’s Eastern Flank

March 18, 2024
Tomáš A. Nagy
2 min read
Photo credit: photographybyog /


The Bucharest Nine (B9) format was established in 2015 in response to the evolving security landscape in Europe, particularly in light of Russia’s aggressive geopolitical revisionism, especially its military actions against Ukraine and illegal annexation of Crimea. It brings together nine Central and Eastern European countries aiming to bolster their defense capabilities and to enhance collaboration with other NATO members. Bulgaria, Czechia, Estonia, Hungary, Latvia, Lithuania, Poland, Romania, and Slovakia use the B9 primarily as a platform to coordinate their positions and exchange views on shared interests, particularly in security, defense, and energy security. Its primary focus is to enhance the security of NATO’s eastern flank and stability of the region, which has been significantly impacted by Russia’s aggression. This prompted the B9 countries to take robust action to address the challenges this poses.

The B9 was established based on two complementary rationales: a strategic rationale to enhance collective security and safeguard the interests of the nine countries through strategic deterrence, and a political rationale to build and accumulate their political capital within NATO. The format has been instrumental for them to advocate increased defense spending, resilience building, and shaping NATO’s strategic deterrence on its eastern flank. It has also been used to emphasize the need for military infrastructure development—including air bases, ports, command centers, and logistical facilities—to ensure a credible deterrence posture vis-à-vis Russia. Since February 2022, the B9 priority has included ensuring Ukraine’s survival as an independent state and supporting its closer integration into the security architecture of the region, including NATO membership. While the format has been less used in EU decision-making processes, the B9 has aligned itself with the EU post-2022 sanctions regime against Russia.

The B9 has maintained a flexible approach, convening meetings as needed and bringing together government leaders and officials to address emerging security concerns. Its influence has been significant, particularly in shaping NATO’s strategic deterrence and advocating key priorities within the alliance. In the future, the B9 is likely to concentrate on the further enhancement of NATO’s footprint on the eastern flank through a greater military presence and key capabilities for strategic deterrence, and also on boosting resilience in the member countries and on supporting Ukraine (and Moldova) with their urgent security needs.

In this perspective, the B9 should: continue to prioritize support for Ukraine, particularly where it can do so without significant material military assistance; advocate the further structural enhancement of Central and Eastern Europe’s integration into NATO’s functional assets; promote greater military mobility, advocate the establishment of a long-term NATO air and missile defense model, and enhancing societal resilience and addressing hybrid threats at the EU level.

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