“Any gear that is forward-deployed both reduces cost and speeds up our ability to support operations in crisis, so we’re able to fall in on gear that is ready-to-go and respond to whatever that crisis may be,” Col. William Bentley, operations officer for the 2nd Marine Expeditionary Brigade, said in a statement Friday on the Norwegian deployment that called the caves classified.

The deployment of new equipment to the Cold War-era caves comes amid renewed tensions between NATO and Russia. Russia shares a 121.6-mile long border with Norway. The border was heavily militarized during the Cold War, and the Russian navy’s Northern Fleet is in Murmansk, about 100 miles from the border.

In October, Norway’s Chief of Defense, Adm. Haakon Bruun-Hanssen, told reporters that Russia has “shown that they are willing to use military force to achieve political ambitions.”