"It makes a lot of sense here," he said. "We like the aspect of the hydrogen technology that it can be produced in a number of ways. We may be able to source a local resource such as natural gas, regular diesel, wind, solar or nuclear energy and convert that to hydrogen right there, in theater, where we need it."

The ZH2 made its debut last October, but the Army and GM have been exploring fuel-cell applications for awhile: first with a with a full-size truck in 2001, and then by including some of Chevy's "Project Driveway" crossover SUV, the Equinox, into the military pool and installing refueling stations around bases.

Project Driveway in 2008 was a 30-month pilot program to glean data from drivers in New York, Washington, D.C. and California (a fuel-cell haven) on how the alternative-fuel SUV performed in the real world. That accumulated data helped pave the way to a partnership between GM and Honda in 2013, and earlier this year, a $170 million joint investment in a fuel-cell-production plant near Detroit.

Last year, GM engineers were able to shrink the size of an HFC power plant and fit it under a customized Colorado ZR2 hood. From there, GM removed the truck's back window and rearview mirror, shifted the cab 400mm to make room for those massive tires, reinforced the front and rear body panels with Kevlar and carbon fiber, and made "slight" adjustments to the vehicle's front- and rear-frame overhangs.

Those giant intakes you see behind the rear doors don't just look radical -- they serve a functional purpose, feeding the 1,000-pound-per-foot-of-torque propulsion system plenty of air for cooling. The ports are designed in such a way that even when the ZH2 is standing still (say, being used as a generator) they can still suck in enough air to keep the truck from overheating.

Oh, and inside there are the Recaro racing seats and Simpson five-point racing harnesses that keep you strapped into the truck. Essentially, GM took an already absurdly capable off-road vehicle (the diesel ZR2 outputs 369-pound-per-foot of torque) and made it even better. It just took 50 years or research and development to get there.

"You don't just start these [initiatives], flip a switch and then go," said Charlie Freese, GM's executive director of fuel-cell business. He should know. Freese has dedicated his entire career to diesel, serving as chief engineer of diesel tech at Ford for two years before moving to head up GM's fuel-cell program in 2008. Prior to that, he spent 11 years at Detroit Diesel in various roles.

Freese sees an interesting contrast between the two power sources. On one hand, diesel can be incredibly efficient, but it always costs more. Then there are the inherent emissions issues. On the other hand, fuel cells are clean tech, but they're prohibitively expensive. Freese wouldn't say anything about price, but the base ZR2 starts at $40,000 before you add the diesel engine (typically a $5,000 option). For comparison's sake, a Honda Clarity FCV sedan has a $63,000 MSRP. Cost could prove a temporary hurdle, as economies of scale can help bring the price down as more FCVs are produced regardless of who's buying them.