The phrase "An army marches on its stomach," often attributed to Napoleon Bonaparte, underscores the importance of logistics in the military. And in the 21st century, keeping up the supply of diesel fuel is one of the most challenging logistical tasks for military forces in the field. Last month, the U.S. Department of Defense (DoD) awarded a contract to a company that says its “hybrid generator” can reduce the amount of fuel used by generators at outposts by more than 50 percent. The company, Earl Energy, uses a rack of batteries coupled to diesel generators—and, if available, solar panels—to optimize fuel consumption. It’s one of a number of projects funded by the Department of Defense to reduce fuel consumption through efficiency and renewable energy.