Marines from the MWTC on top of Denali in Alaska, the highest point in North America. MWTC Temperatures during the Korean War’s decisive battle at the Chosin Reservoir in late 1950 were as low as negative 35 degrees Fahrenheit. The terrain was more rugged than most American troops had ever seen.

Allied forces were outnumbered and encircled. "We've been looking for the enemy for some time now. We've finally found him. We're surrounded. That simplifies things,” the then commander of the 1st Marine Regiment Col. Lewis Burwell “Chesty” Puller famously said.

The Marines took heavy losses during that battle, primarily due to the elements and otherwise treacherous conditions.

The lessons learned at the Chosin Reservoir led to the inception of what is today known as the Marine Corps Mountain Warfare Training Center, in 1951. It's located in an isolated 46,000-acre tract deep inside Toiyabe National Forest in northern California.

Nestled in a valley between rugged mountain ranges in California’s Sierra Nevada, MWTC all but mirrors conditions Marines faced on that frozen battlefield decades ago. Today it is the premier training ground for Marines heading into mountainous, high altitude, and or cold weather environments, like the site of the Corps' weapons stocks in Norway — or, until recently, the alpine regions of Afghanistan.

Business Insider visited the Marine Corps premiere facility for preparing its soldiers for the rigors of alpine warfare. Located high in California's Sierra Nevada, not far from Yosemite National Park, it is one of the Corps' most unique installations — set amid spectacular natural beauty.