NATO members along the Alliance’s eastern flank are working to strengthen their borders against potential attacks from Russia.
The countries have launched two major initiatives to this end. In January 2024, Estonia, Latvia and Lithuania announced the Baltic Defense Line (BDL). Poland announced its Eastern Shield in May 2024. Both efforts call for the nations to build a network of reinforcements along their borders with Belarus and Russia that include anti-tank barriers, trenches and other fortifications. The set of layered defensive measures aims “to effectively prevent, disrupt and deter potential enemy incursions,” a letter from the nations to the European Union said. The European Commission has pledged some $88 billion in financial support to the programs, including preferential loans, according to multiple news reports.
In February 2026, Estonia announced it had begun to procure 600 modular bunkers as part of the BDL. Plans include a sophisticated network of trench systems, bunkers, observation posts, ground sensors, anti-armor obstacles and surveillance systems along more than 1,600 kilometers of those nations’ borders, according to a report from the International Institute for Strategic Studies (IISS). The complex network is aimed at buying time for Allies to deploy reinforcements under NATO’s Article 5, the NATO principal that if an Alliance member is the victim of an armed attack, each Ally will consider the action an attack against all member nations. By slowing and canalizing attacking forces, the BDL aims to give NATO’s Very High Readiness Joint Task Force the time needed to cross from staging areas in Poland and Germany to the Baltic front.
“The first bunkers for the Baltic Defence Line have already been delivered, and their installation is progressing step by step in Southeast and Northeast Estonia,” Asko Kivinuk, deputy director of the Estonia Centre for Defence Investment, told the website Defense News. “The experience gained gives us the confidence to move forward with a larger-scale procurement.”
Latvia is also in talks to buy bunkers. Kivinuk noted that joint procurement can save the countries money through economies of scale. The BDL is expected to be completed by the end of 2027.
Defense leaders describe Poland’s Eastern Shield initiative as the largest undertaking in that country’s history to beef up protection along its border and NATO’s territory close to Russia, according to Newsweek magazine. Under Eastern Shield, Poland will weave in trenches and antitank obstacles with natural barriers like swamps and forests, plus anti-drone systems and shelters, along some 700 kilometers of Poland’s border, according to IISS.
The country is procuring land for Eastern Shield and will expand rapidly in 2026, said Polish Army Col. Marek Pietrzak, general staff of the Polish Armed Forces. Poland also is investing heavily in modern surveillance and strike capabilities, including anti-aircraft and counter-drone systems, unmanned aerial platforms, mine-laying vehicles and reconnaissance assets. By the end of 2026, Poland will have built defenses along roughly 38% of its eastern and northern borders, Newsweek reported.
All four nations increased air patrols along NATO’s eastern edge after Russian drones crossed into Poland airspace in September 2025. In addition, NATO announced operation Eastern Sentry to counter increased Russian threats.
“Full-scale war is now a reality in Europe,” Polish Lt. Gen. Karol Dymanowski, vice chief of general staff of the Polish Armed Forces, told a visiting NATO delegation in November 2025. “Hybrid warfare is a constant, and strategic competition is intensifying — we are not at war, but not at peace either, and we need to scale deterrence and defense accordingly.”