Selfies and secretaries of the Navy aren’t something you usually think about together. But the signature photo technique of today’s teenagers seems to have infiltrated even the highest echelons of U.S. security.

Secretary of the Navy Ray Mabus squeezed in a selfie with 16 Navy ROTC midshipmen at Arizona State University on Thursday after giving a speech about energy and security. (Disclosure: ASU is a partner with Slate and the New America Foundation in Future Tense.)

But the selfie was just a brief diversion in Mabus’ discussion about making alternative energy use a top priority in the U.S. Navy and Marine Corps.

Environmentalists may laud Sec. Mabus for his Earth-friendly agenda, but finding alternative energy sources to fuel ships and aircraft is about war, not climate change, Mabus said.

“We’re doing this to become better warfighters. That’s the only reason,” he said. “There are some good side effects—things like reducing carbon and things like climate change—but that’s not the reason we’re doing it. We’re doing it to reduce a vulnerability.”

Using energy as a political weapon is not a new tactic, and Mabus’ words came with a not-so-thinly-veiled stab at Russia and its inflation of natural gas prices over tensions in Ukraine. “Europe is a large customer for Russia, but Russia depends on oil and gas revenues for over half its government’s budget,” he said. “Imagine the impact alternative power and conservation measures might have.”

The U.S. Department of Defense is the largest consumer of fossil fuels in the world. Each year the Department of Defense budgets approximately $15 billion for fuel. In fiscal year 2011-2012, spikes in the price of oil cost the Department of Defense an additional $3 billion in unbudgeted fuel expenses, Sec. Mabus said.

For the Navy and Marine Corps, every $1 increase for a barrel of oil costs an extra $30 million, he said. “There aren’t many places to go and get that [money]. You have to change your operations, so you steam less, you fly less, you train less.”

Reducing operational capabilities may not be such a good idea especially when some predict instabilities due to climate change are nigh. The Navy even has a special Task Force Climate Change to address security threats that could crop up from the rise in sea level and opening of Artic sea passages in the melting polar caps.

Mabus said the Navy and Marine Corps are on-track to meeting the energy goals he laid out in 2009, which includes supplying half of all naval energy needs with alternative energy sources.

“We are going to meet these goals. It’ll make us better at our jobs. It’ll make us better warfighters. And it will make us and the world far more secure.”

Correction, April 29, 2014: The photo credit in this post originally misidentified the photographer. The photo was taken by MC1 Arif Patani, not MCC Keith DeVinney.