The Salpa Line included more than 700 concrete or rock-cut bunkers, approximately 3,000 field fortifications, and roughly 217 miles of fighting and connecting trenches. Its antitank defenses extended for more than 124 miles.
Part of the historic Salpa Line defensive fortifications. Photo: Wikipedia.org
Modern Finnish planners are not simply rebuilding those massive fixed defensive lines. Instead, they are developing positions that can be constructed relatively quickly, adapted to local terrain, modified after testing, and concealed from drones and other surveillance systems.
The BASE program also indicates that fortification skills are being reintroduced systematically into military training. Finnish troops are learning not merely to occupy a bunker, but to construct, conceal, defend, lose, and retake a complex position while continuing to operate under persistent observation and attack.
The return to underground fortifications illustrates a wider shift taking place across European militaries. Technologies once expected to make warfare faster and more mobile have instead made concealment, overhead protection, prepared defensive positions, and the psychological endurance required to remain in them increasingly important.
Sources: Adapted and expanded from Tero Tuominen, “Liikkuvasta taistelutavasta maan alle – linnoittaminen yleistyy taas,” published by Reserviläinen on July 17, 2026, and Kalle-Emil Ronikonmäki, “‘Sodankäynti on muuttunut’ – Nykypäivänä vaaditaan uudenaikaista linnoittamista,” published by Ruotuväki on April 10, 2026.