Last month, the commander of Fort Bliss, a vast United States military complex that straddles the Texas-New Mexico line, announced plans to build a solar farm.
The array will use 94,000 photovoltaic panels to generate 20 megawatts by 2015, or about 14 per cent of the energy used by the 35,000 soldiers on base.
Major General Dana Pittard says the Army wants 65MW by 2018, making Fort Bliss a "net zero" facility, able to generate all its energy needs on-site and eliminate carbon emissions.
The scheme is the largest renewable energy project in US military history. Fort Hood, also in Texas, is hard on Pittard's heels. Given the Pentagon's propensity for burning aquifers of fuel - the first casualty of war is arguably conservation - it comes as a surprise to learn men in khaki think green.
Water conservation, tree planting and recycling waste are also big at Fort Bliss, challenging the military's profligate mindset. The Air Force is adopting non-tactical electric vehicles, and soldiers in Afghanistan use solar panels to power radios and mortar pits. Even new weapons systems must be more sustainable, using "less energy, water and toxic chemicals" while producing "fewer emissions", according to a report released this year.
The new mantra is energy conservation and security, Pittard told the El Paso Times. "That's what we hope our soldiers take with them as they go to other installations and move into society."
The US military is the largest single consumer of oil and energy on the planet, with an annual bill of US$4 billion ($4.7 billion). About half goes to the Air Force. Jet aircraft are the worst offenders. A B-52 bomber, with eight engines, burns 1900 litres of aviation fuel a minute. In 2006 the US Air Force consumed 9.8 billion litres, as much as it did in World War II.
Citing Department of Defence figures, the Energy Bulletin says that while energy use per person was 3.8 litres a day in WWII, by the Vietnam War this had climbed to 34 litres, continuing to 38 litres for the first Gulf War and 58 litres a day in 2007 during the Iraq and Afghanistan wars, making the US GI "the most energy-consuming soldier even seen" in war.
Soaring oil prices have made this unsustainable. The Pentagon wants 25 per cent of its energy sourced from renewables by 2015. Ultimately, the sea change is driven by fears fossil-fuel dependence threatens the US war machine.
"The goal is mission capability," says DoD spokesman Mark Wright. "To make soldiers more self-sufficient. Less dependent on logistical supply lines."
In forward operating bases in Afghanistan, for instance, generators supply power. Fuel must be trucked in by convoys vulnerable to attack, pushing up costs and tying down troops. Microgrids, that match energy generation to use, can reduce fuel use and cut convoys.
"The more efficient you are, the less tied down you are to maintaining communication and supply lines. Which gives commanders more tactical and operational freedom. And that's the real goal we're going for."
Sustainability is intended to cut across both installation and tactical spheres, that is activities within the US or abroad. Microgrids enable US bases to be free of civilian power grids if they go down in, say, a storm like Hurricane Sandy or - the latest worry - a cyber attack.
Kicking oil is a herculean task for a military colossus that has long splurged on cheap oil, says Phyllis Cuttino, who directs the Project on National Security, Energy and Climate at the Pew Research Centre. "Now the military understands US security is explicably linked to energy."
Given the US lacks a national energy policy, carbon targets or a renewables standard, which are left to innovative states such as California, Cuttino says the military has come a long way, partly because of operational awareness wrought in battle, and convoy vulnerabilities when it comes to supplying soldiers with fuel and water. "The most aggressive clean energy standards outside California are in the DoD. They are poised to take significant steps, even in a time of budget cutbacks."
Besides cost savings, there are also commercial benefits. Take biofuels. Despite resistance from the fossil-fuel lobby, the focus is on third-generation biofuels, a development commercial airlines are keenly watching.
Ironically, US intelligence reports say climate change, driven in large part by fossil-fuel use, will "accelerate" instability and wars.
In March, the head of the US Pacific Command, Admiral Samuel Locklear III, told the Boston Globe climate change was the worst threat in the region, citing climate refugees and humanitarian relief missions. "If it goes bad you could have hundreds of thousands or millions of people displaced, and then security will start to crumble pretty quickly."
War is hell, of course, and no amount of Pentagon spin about net zero energy can hide darker undercurrents. It is hard to avoid the reality that US military activity is a huge source of CO2 emissions and other toxic pollution such as depleted uranium from spent munitions.
Fort Bliss may be clean and green, but so is Guantanamo Bay. The Pentagon boasts the notorious US prison - where more than 100 detainees are currently on a hunger strike, prompting calls for its closure - is " completely self-sustaining", with some power generated by four huge wind turbines.
Homeland Security says Brad Lander was arrested for assaulting and impeding officers.