FRIGAARD CAVE, Norway -- Lit by fluorescent lights lining the ceiling, the canvas-walled corridors looked even longer and more cavernous than they did full.
For a rare few days, the caves were mostly empty, the hundreds of combat vehicles, backhoes and trucks they normally held parked in neat "sticks," or columns, outside.
Logistics Marines flown in just for the purpose were in the middle of hustling all the gear out of the caves, performing minor upkeep, and returning it to storage, all with a stopwatch running.
Known as a Strategic Mobility Exercise, or Stratmobex, the drill gave the Marines the chance to test their reflexes in case of a major combat contingency or other crisis that might require them to man the vehicle and weapons with minimal notice.
As the world changes and more attention shifts to Europe, planners are exploring the possibility of expanding the gear cache stored in the caves -- possibly even doubling or tripling its capacity.
The stockpile is stored and maintained under a bilateral agreement between the Marine Corps and Norway that dates back to the Cold War. It's housed in a chain of six caves that winds through the Trondheim region of central Norway. In all, there are six caves and two airfields. Three of the caves hold everything from rolling stock to towed artillery, and another three are packed full of ammunition, officials said.
Gear from Marine Corps Prepositioning Program-Norway, which the Corps calls "McPippin," has been used to equip units for exercises in Europe and Africa over the years, but it also has been regularly sent to war.
"The caves were nearly emptied for [Operation] Iraqi Freedom," said Maj. Tom Stona, a Marine prepositioning programs officer based at the Pentagon.
When Military.com visited Norway in May, officials had just sent ammunition from the caves to support the ground fight against the Islamic State in the Middle East, Stona said. Norway-based gear has also been used for humanitarian assistance and disaster relief missions around the world.
While the equipment is kept up with meticulous care by a Norwegian team -- a Marine light armored vehicle crewman said he had never seen an LAV as well maintained as the one pulled out of the caves for him -- the gear cache is evaluated for major changes every few years.
The last time that happened was 2012, Stona said. At that time, with the primary war effort in Afghanistan nearing its close, Marine planners refashioned the equipment stockpile from a more general purpose array to a "MCPPN MAGTF," he said, using the acronym for Marine air-ground task force.
The caves currently hold enough to equip a fighting force of 4,600 Marines, led by a colonel, with everything but aircraft and desktop computers. But the stockpile soon could get bigger -- a lot bigger.
"Our customers, [Marine Forces Europe] and [Marine Forces Command], their desire is to be able to aggregate a [Marine Expeditionary Brigade,] so MCPPN is going to seek to facilitate that with whatever equipment we can get over here to help stand a MEB up as quickly as possible," Stona said.
Marine Expeditionary Brigades are one of the largest fighting units that the Corps sources, and can consist of 8,000 to 16,000 Marines, or even more. At this point, what a MCPPN MEB might consist of is not entirely clear.
"You ask two people what a MEB is, you get two different answers," Stona said.
Planners are completing an analysis of the current gear cache that should wrap up in the next 12 months. The strategic mobility exercise gave them a chance to evaluate not only what was stored, but how. Stona said officials are exploring the possibility of storing the equipment in response-ready packages, so it could be unloaded and sent to a fight or disaster even more quickly, though maintenance challenges may make such a move impractical.
Regardless, the Norwegian government will have the last word on how big the stockpile gets and what is stored.
"We do a feasibility of support with the Norwegians, and tell them, 'We'd like you to store this. Do you have the space?' and they will give us an answer," Stona said. "So that will happen as we continue to tailor."
Officers with the prepositioning program declined to speculate on why the Corps wants to grow the stockpile of gear to support a bigger force. But with more military attention focused on Europe as Pentagon efforts to reassure allies and deter Russian aggression come to the forefront, the number of exercises using the cave-stored gear has grown "exponentially," Stona said.
For the first time in January, the service deployed a rotational force of about 300 Marines to the Trondheim region on a trial basis to train with Norwegian troops and exercise the gear.
Lyle Layher, prepositioning officer for Marine Corps Forces Europe and Africa, said there is no doubt the store of combat gear will see daylight even more often in coming months.
"Now that we have a rotational force that comes here, and our relationship with the Norwegians is growing, I think that the opportunity to train on a more regular basis is going to happen," he said.