Environmental advocates have branded retired Marine Gen. James Mattis as the “lone green hope” among the nominees announced thus far by President-elect Donald Trump. They pin their hopes on Gen. Mattis‘ 2003 plea that Navy researchers “unleash” the Marine Corps “from the tether of fuel.” However, his motivation to seek alternative energy probably had nothing to do with the debate over climate change.

Energy has been described as both the “lifeblood of our war fighting capabilities” and its “Achilles heel.” Fuel keeps planes in the air, ships at sea, and troops in the field, but it also “tethers” these combat elements to their sources of supply — restricting their range and mobility and consuming limited resources for transportation and force protection.

During the war in Iraq, fuel supply problems slowed the advance of U.S. forces and ground supply convoys provided attractive targets for insurgent forces — leading to both higher costs and higher casualties. It was under these conditions, while serving as the commanding officer of the First Marine Division in Iraq, that Gen. Mattis issued his plea to be freed of the fuel “tether.”

The general was motivated by the desire to improve military capability and reduce casualties. That is in sharp contrast to the Obama administration’s politically motivated “clean energy” initiatives, which were driven by arbitrary consumption targets and intended to “jump-start” the market viability of green technologies.

This is not to say green energy cannot play a role in defense. For instance, energy that can be generated at the point of use (such as solar power) can reduce reliance on logistics or lighten the load of disposable batteries carried by ground forces — making small units and individuals lighter, more mobile and less vulnerable to supply disruptions.

In remote and contested environments, as well as in challenging terrain where access to external energy sources is limited, enabling combat units to operate autonomously is critical. Hybrid generators and solar blankets have demonstrated potential to reduce reliance on petroleum and provide power for individual electronic devices, radios, and even small combat outposts for longer periods of time.

However, the vast majority of the Pentagon’s fossil fuel needs are for ships, tanks and aircraft. The energy demand and intensity of these systems far exceeds what can be provided by solar power and other on-site methods of power generation. The military thus remains dependent on fossil fuels to meet its operational energy demand.

Even here, the Obama administration insisted there was a green alternative: “advanced biofuels.”

Unfortunately, when it comes to supporting military capability, advanced biofuels are the free-range chicken of the energy world — an expensive alternative with little to no benefit. Whether made with fossil fuels, soybeans or beef fat, all liquid fuels serve the same purpose. A plant-based fuel of the same volume and energy density as its conventional counterpart is no less susceptible to attack and no less cumbersome to transport.

Nor would biofuels make the Pentagon less dependent on foreign oil, since a primary factor in deciding where to purchase fuel is its proximity to the battlefield. The best-case scenario for advanced biofuels, as we know them now, will be to substitute dependencies while retaining the same risks.

The next administration will need to decide where the military’s resources, capabilities and budget can be applied to the greatest effect. Given that defense spending has been cut by approximately 25 percent over the last five years, and the military is struggling to meet even minimal levels of readiness, green energy for green energy’s sake is an unnecessary distraction from the real issues facing our military today.

If Gen. Mattis‘ plea was an indication of anything, it is his desire to enhance combat effectiveness and reduce American casualties. His interest should be what’s best for the Red, White and Blue. Green is a distant second, at best.