Lance Cpl. Ryan Foret, right, and Lance Cpl. Richard Orozco, strain as they reach the top of a jungle slope carrying a Marine on a stretcher made from branches and uniform tops during the Jungle Warfare Training Center's vaunted E-Course. The Marines from 3rd Platoon, Company I, 3rd Battalion, 2nd Marine Regiment based out of Camp Lejeune are in Japan on a six-month rotational deployment through the Unit Deployment Program. The program was scaled back during the wars in Iraq and Afghanistan but is now being revamped. (Matthew M. Burke/Stars and Stripes)

Lance Cpl. Kyle Littell wades through the waist deep ''peanut butter''' mud during the Jungle Warfare Training Center's E-Course in March 2015. (Matthew M. Burke/Stars and Stripes)

Marines from Company I, 3rd Battalion, 2nd Marine Regiment based out of Camp Lejeune, N.C., march into the jungle under overcast skies at the beginning of jungle warfare training in Okinawa in March 2015. (Matthew M. Burke/Stars and Stripes)

Then-Cpl. Donald Horn, now a sergeant, left, looks at his map during a land-navigation training exercise at the Jungle Warfare Training Center at Camp Gonsalves in OkinawaÕs remote north in March 2015. (Matthew M. Burke/Stars and Stripes)

A Marine gets tangled in concertina wire during the E-Course at Okinawa's Jungle Warfare Training Center in March. (Matthew M. Burke/Stars and Stripes)

A Marine performs a hasty rappel in the pouring rain at Okinawa's Jungle Warfare Training Center in March 2015. A hasty rappel is essentially running headlong down a steep rockface holding a single strand of rope, without a safety harness. (Matthew M. Burke/Stars and Stripes)

A Marine from Company I's weapons platoon creeps through the mud and jungle foliage during the Jungle Warfare Training Center's E-Course in March 2015. (Matthew M. Burke/Stars and Stripes)

Company I Marines rest by a jungle stream during a break from jungle warfare training at the Jungle Warfare Training Center in northern Okinawa in March. The Marines came to Japan on a six-month rotation to learn to survive and fight in the jungle's harsh environment. (Matthew M. Burke/Stars and Stripes)

Lance Cpl. Andrew Luna wades through muddy water during Jungle Warfare Training on Okinawa in March 2015. Luna, who was nearly finished with Marine Officer Candidate School when he broke his arm in 2011, decided to enlist in the Corps to 2013. He still wants to be an officer, but ''you can lead enlisted men a lot better knowing what they go through,'' he says. (Matthew M. Burke/Stars and Stripes)

Lance Cpl. Andrew Luna, left, carefully moves into an unsecured building teeming with enemies during urban assault training at Camp Fuji's MOUT town in April. He is covered by Lance Cpl. James Spooner. Luna, who was nearly finished with Marine Officer Candidate School when he broke his arm in 2011, decided to enlist in the Corps to 2013. (Matthew M. Burke/Stars and Stripes)

Lance Cpl. Andrew Luna, left, watches intently as Cpl. Logan Hampton, center, plots call-for-fire coordinates at the Rodriguez Live Fire Complex in South Korea. (Matthew M. Burke/Stars and Stripes)

Lance Cpl. John Brooks Jr., pulls himself over an empty concrete pool during a ropes course at the Jungle Warfare Training Center in March. (Matthew M. Burke/Stars and Strip)

Lance Cpl. James Spooner emerges from thick jungle undergrowth during a land-navigation exercise at the Okinawa Jungle Warfare Training Center in March. (Matthew M. Burke/Stars and Stripes)

Marines from Company I's weapons platoon enter a pool of murky jungle water during the Jungle Warfare Training Center's E-Course in March. (Matthew M. Burke/Stars and Stripes)

Lance Cpl. Eduardo Rodriguez of Company I's weapons platoon surveys a maze of concertina wire before it is his turn to dive in during the E-Course at Okinawa's Jungle Warfare Training Center in March 2015. (Matthew M. Burke/Stars and Strip)

Lance Cpl. Jake Bombrys jumps into a concrete pool, filled with putrid jungle water, and covered with plywood. With barely enough room to breath, the 3rd Platoon Marine had to traverse underwater obstacles. The obstacle is part of the Jungle Warfare Training Center's E-Course. (Matthew M. Burke/Stars and Stripes)

Then Cpl. Donald Horn, now a sergeant, left, watches Lance Cpl. Jacob Mathes as he ties a knot during training at the Jungle Warfare Training Center in March. (Matthew M. Burke/Stars and Stripes)

Second Platoon's Cpl. Robert Edwards-Morris holds the body of a still wriggling poisonous habu snake. The Marines were taking part in jungle survival training for at Okinawa's Jungle Warfare Training Center in Marc 2015. (Matthew M. Burke/Stars and Stripes)

Cpl. Curtis Beam directs his squad during casualty evacuation drills using two MH-60S helicopters from Helicopter Sea Combat Squadron 12 at Okinawa's Jungle Warfare Training Center in March. (Matthew M. Burke/Stars and Stripes)

Third Platoon Marines traverse a jungle pool, rifles at the ready, using their packs and poncho liners to make an impromptu raft during jungle warfare training in Okinawa in March 2015. (Matthew M. Burke/Stars and Stripes)

Lance Cpl. Khadeem Jeffers, a mortar man with Company I's weapons platoon, breaks through dense jungle foliage at the end of the arduous E-Course on Okinawa in March 2015. (Matthew M. Burke/Stars and Stripes)

A Marine feigning an injury is carried to a waiting MH-60S helicopter from Helicopter Sea Combat Squadron 12 during casualty evacuation drills at Okinawa's Jungle Warfare Training Center in March 2015. (Matthew M. Burke/Stars and Stripes)