In the past it was always assumed that any Russian invasion would roll straight into the Baltic states. In recent years, however, in addition to benefitting from the presence of NATO battlegroups, Estonia, Latvia and Lithuania have been mounting a major initiative to harden their borders against any Russian aggression with the formation of the Baltic Defence Line.
Everyone in the West has been paying attention to Russia and the war in Ukraine, but if you look closely the three Baltic states – Estonia, Latvia and Lithuania – are paying really close attention. Their defence considerations are existential. The rest of us should pay attention to how the Baltic militaries are paying attention. They are building the Baltic Defence Line: a belt of obstacles and other defensive features along their border with Russia and Belarus.
A similar project, ‘Tarcza Wschód’ (‘East Shield’), is underway in Poland.
The genesis of the project was an agreement by the three countries’ ministries of defence in January 2024. Given the populations in the border areas and the amount of money being spent (EUR 303 million over five years in Latvia alone), keeping the outlines of the project secret is pointless. Although full details are not forthcoming, significant public documentation on government websites has described many features of the Baltic Defence Line, while the features do appear to vary somewhat by country. Very similar graphics (Latvian here) and contracting documents allow us to synopsise the obstacle belt. Features include:
An important but under-reported aspect of the Baltic Defence Line is use of the existing terrain. The three Baltic states were, in the past, not considered highly defensible terrain. Numerous armies have used them more as a highway than as a defensible barrier in themselves. The old routes from Berlin to St Petersburg run through the region. However, this does not mean that the topography does not have defensive aspects. Dense forests reduce mobility and force dismounted operations, but also provide some degree of overhead cover. Swamps and bogs in the region have also proven fatal in the past, including to four US Army soldiers in an armoured vehicle in Lithuania during an exercise in 2025.
There are numerous ways to both overtly and subtly improve the defensive aspects of terrain. One of these is to increase the size of wetlands. Lithuanian media reports such efforts as part of a joint defence and environmental restoration project. Polish media reported similar work on peat bogs in Latvia.
How would such a defensive barrier actually work in the event of a Russian invasion? Applying both classical and modern principles of warfare, one can see what the missions of the Baltic Defence Line are in real-life scenarios.
First, let’s discard what such a system is not. Although there are numerous bunkers for troops, this is not some sort of fortress system designed to protect large numbers of forces. For one thing, the Baltic militaries do not have large numbers of forces and certainly do not want to tie them down on the border. This is not the First World War.
The key goal is what the combat engineers refer to as ‘counter-mobility’. The layers of barriers are not designed to permanently stop a Russian onslaught; they are designed to reduce the mobility of invading troops. A well thought out counter-mobility plan achieves several objectives:
There are less directly military aspects to this fortified buffer zone. There’s a political aspect to all of this, too. When I was first in Estonia in 1992, there were legitimate fears that people would look out of the window in the morning, in the national capital Tallinn, and see Russian troops on the streets. For about the first 20 years after independence, it was believed that Russian troops would be in charge of the three capitals (Tallinn, Riga and Vilnius) before anyone in the rest of the world could do anything. The small and poorly equipped Baltic militaries of the 1990s could only mount token resistance.
Nowadays, in light of Russia’s annexation of Crimea and invasion of Ukraine, the Baltic nations and Poland are each protected by NATO battlegroups, but by putting the first likely and very loud contact with Russian troops on the actual border, or at least a 5-10 km deep zone along the border, it buys time to mobilise not just more allied troops but also opinions on the world stage.
There also appears to be significant local engagement with communities and populations along the border. Whether this is laying the groundwork for partisan resistance or not, any historian of the region must take note that there is a history of Baltic rural areas being ungovernable and controlled by partisans. All three countries have paramilitary reserve elements that will form part of the resistance. The old joke that there will be a rifle behind every tree may be an exaggeration, but there are a lot of trees and the defensive co-ordination efforts in the border zone will probably get a lot of people thinking about which tree they are going to get behind. Indeed, if bunkers are bypassed by a Russian advance, it may mean a rear-area security threat to Russian supply lines.
The Baltic Defence Line shows that Estonia, Latvia and Lithuania, as well as NATO, are adopting a total defence strategy not unlike that of Finland. The old notion of a war to liberate the Baltics after an initial defeat is gone. NATO troops are embedded as a figurative tripwire, but now there are literal tripwires. Fifty years of Soviet domination and centuries of earlier Tsarist oppression weigh heavily on the Baltic states. They will not go without a fight.
