Hidden in central Oahu is a military range run by the Army's 25th Infantry Division. The focus: Teaching soldiers jungle warfare.
"A lot of the training we provide is realistic and is applicable in the event that they ever have to find themselves operating in a jungle environment," said staff Sgt. Michael Johnson, an instructor who teaches soldiers a skill-set the Army once valued then abandoned.
Lightning Academy Commander Capt. Matthew Jones said since the United States has been militarily involved in the Middle East, "we kind of lost our fundamentals and our knowledge about how to fight in a jungle."
But since 2013, the military has pivoted back to jungle training.
The 25th Infantry Division's Jungle Operations Training Course is the only one of its kind on U.S. soil.
Soldiers learn to traverse mountainous terrain, and slog through streams.
"Not only is the enemy a threat, the environment's a threat, too," Johnson said.
To maneuver through the jungle, soldiers learn to overcome obstacles. The mobility training includes rappelling down cliffs, including a 75-foot drop.
"Not only are they learning a valuable skill of being able to rappel, they also get a little confidence boost that eliminates that fear of heights," Johnson said.
Water training forces participants to cross rivers over ropes or on packs and ponchos fashioned into flotation devices.
There's a combat course, too, and soldiers also learn basic survival skills, like trapping food, purifying water, and starting a fire.
Instructors incorporate techniques learned at jungle training sites in France and Brazil.
"Part of our mission is to serve as the U.S. Army's premier Pacific training venue," Jones said.
The soldiers who enroll are mostly from the 25th Infantry Division, but members of other military branches and instructors from jungle schools in other parts of the world have gone through the three-week training, which is no walk in the park.
"There's surprise at how hard it is," Jones said.
For now, jungle training is voluntary and participants either pass or fail.