Forts are back in fashion. Ukraine's counteroffensive last year was thwarted by the so-called Surovikin Line: a vast series of Russian minefields, trenches, anti-tank obstacles and old-fashioned barbed wire, among other obstacles. As Ukrainian troops slowed to clear mines, bridge ditches and bulldoze obstacles, they were observed by drones and hit by a hail of anti-tank missiles and suicide drones. This area was so unknown that Valery Zaluzhny, then Ukraine's top general, asked his staff to dig up “Breaching Fortified Defense Lines,” a book by a Soviet major general. It was published in 1941.
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The NATO armies have taken notes. In January, the defense ministers of Estonia, Latvia and Lithuania announced they would build a series of “anti-mobility defense installations” along their borders with Russia and Belarus, collectively known as the Baltic Defense Line. “Reinforcement measures have played an important role. in wars in our region in history,” said Susan Lillevali, an Estonian defense official, pointing to the example of the Soviet-Finnish war. “We also studied the Russian war in Ukraine,” added Lt. Col. Kaido Tiitus, commander of the Estonian Defense League, a volunteer organization. “Our most important lesson is that we must find a way to stop the advance of Russian armored vehicles. units.” The Baltic states will not be assured of the promise, made by Vladimir Putin in a February 8 interview with former Fox News journalist Tucker Carlson, that he had no plans to invade the Baltic states, Poland or anywhere else outside Ukraine to fall.
Estonian officials estimate that their part of the border will need about 600 concrete bunkers, each 35 square meters, each of which could house about 10 soldiers and could be hit by a large shell. Prototype bunkers are being developed and construction is expected to begin next year, at a cost of approximately €60 million ($65 million). The goal is not to create an impregnable fortress, but to slow down invaders, exhaust them, and buy time to bring in reinforcements. If Latvia and Lithuania were to build bunkers with a similar density, they would need 1,116 and 2,758 bunkers respectively, calculates Lukas Milevski, an expert at Leiden University in the Netherlands.
The catch is not military engineering, but democratic consent. “The most important part is an agreement with the landowners,” says Ms. Lillevali, noting that most border areas are privately owned. She says there is little sign of resistance from the area's Russian-speaking minorities. Locals may be reassured by the fact that the armed forces do not plan to stockpile explosives near the strongholds in peacetime, nor install anti-personnel mines, which are illegal under the Ottawa Treaty. An attempt in the Estonian parliament last year to withdraw from that treaty produced little progress.
The appeal of fortifications is easy to see. European officials are concerned that Russia's breakneck rearmament is outpacing European efforts to boost weapons production. Baltic leaders have emphasized that even small Russian advances could be existentially threatening to their states. “It cannot be ruled out that Russia will test Article 5 and NATO solidarity within a period of three to five years,” Troels Lund Poulsen, the Danish Defense Minister, warned on February 9. “That was not NATO's assessment in 2023. This is new information that is now emerging.” In light of this feverish mood, the Baltic defense line is both a military and a political statement.
But Russia's successful defense has also led to a broader rethink. Russian fortifications in southern and eastern Ukraine were the most extensive in Europe since World War II, according to analysis by the Center for Strategic and International Studies, a U.S. think tank. They are probably matched only by the minefields and obstacles on the inter-Korean border. In November, Volodymr Zelensky, the Ukrainian president, urged his commanders to speed up construction of defenses in the east. Poland is also building fortifications and shelters along the border with Russia and Belarus, an ally of the Kremlin.
This poses a dilemma. NATO militaries have long favored a more elastic defense in depth, with troops withdrawing when necessary and destroying the enemy on more favorable terrain. That is incompatible with defending every inch of NATO territory. But with an “operationally static defense,” Mr. Milevski notes, “it is much more important to ensure that the blow, when it comes, is as weak as possible.” That places a much greater emphasis on using heavy firepower to strike deep behind Russian lines to deplete the attacking force and break the chain of command and logistics. In short: heavy bombardment on Russian soil. “Western political leaders,” he warns, “can be squeamish about such attacks.”
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