The vast cold-war complex on Muskö, about 25 miles from Stockholm, features cavernous underground docks that can shelter warships, miles of tunnels, offices and hospital and was built to survive a nuclear attack. The top-secret base was completed in 1969 and has not been fully operational for 25 years but Sweden has decided it is time to return to the granite-encased base as it builds up its defences in response to a perceived threat from Moscow.
Swedish naval command said the new location would offer greater freedom of manoeuvre for its maritime defence operations.
Rebecca Landberg, head of communications for the Swedish navy, said: “The Muskö base is unique from a fortification perspective, it is an underground area as big as the old town in Stockholm.
“The naval command must have resilience and function even under attack, so Muskö is the best option.
“The armed forces need to adapt their operations to meet the challenges posed by the deteriorating external environment.”
Sweden slashed military spending from about 2.5 percent of GDP in 1990 to barely 1 percent by 2010 as the end of the Cold War reduced the threat of attack from the east.
But Niklas Granholm, a senior analyst at the Swedish Defence Research Agency, said the occupation and annexation of Crimea by Russia in 2014 “changed things completely”.
He said: “It showed that this is what Russia does to its smaller neighbours.
“Now it is proving a difficult and long-term task to rebuild the armed forces.
“The move is based on the calculation that the Russians could use powerful weapons which demand the level of protection that only Muskö can provide.”
The shipyard on Muskö was sold to German engineering company Thyssen Krupp and although it ceased to play a central role in Swedish defence in the 1990s the navy never left the island entirely.
But the facilities have fallen into disuse and it will take several years for the base to be comprehensively modernised and renovated. The underground command centre will not be fully equipped until 2021 or 2022.
Russia’s Baltic Fleet was in action last week as helicopter crews delivered rocket and bombing strikes against a notional enemy’s surface ships and high-speed craft in a series of real-time drills.
A fleet spokesman said: “The crews of the deck-based Ka-27PL anti-submarine warfare helicopters, Ka-29 shipborne combat and transport rotorcraft and Mi-24 gunships from a Baltic Fleet naval aviation formation accomplished combat exercises during their training flights to overcome the air defenses of a group of the notional enemy’s combat ships and deliver bombing and rocket strikes.
The helicopter crews approached the targets from different directions while maneuvering by their speed and altitude to complicate the air strike’s repulsion by the adversary warships.