Army operations span a diverse range of environments and tasks, from base infrastructure under lesser threat, to expeditionary operations and sustained campaigns in hostile zones. Supplying energy to these diverse missions is increasingly challenging; constraints and threats to the supply of energy, water and other resources are growing in scope and complexity both abroad and at home. Going forward, the fullspectrum operations of the future—conducted across wide areas and austere environments—will require more energy and resources but with greater efficiency and portability at lower overall costs.nergy security and sustainability are operationally necessary and financially prudent and are key considerations for U.S. Army installations, weapon systems and contingency operations. “Energy security” means that the Army retains access to energy and can continue to operate when catastrophe strikes and energy supplies are disrupted, cut off or difficult to secure. To remain operationally relevant and viable, it must reduce its dependency on energy, increase energy efficiency and implement renewable and alternate sources of energy force-wide. It must also have leaders who are cognizant of, and sensitive to, the complexities of enduring energy and resource requirements. To balance these requirements against the growing constraints on energy worldwide, the Army is applying a key principle to the breadth of operational and organizational settings: sustainability. This sustainability principle is designed to ensure that the Army of tomorrow has the same access to energy, water, land and other natural resources as that of today through the reduction of demand/consumption, the diversification of the energy supply and increased self-sufficiency. The Army is taking steps to reduce its reliance on fragile energy infrastructure and logistical mechanisms that add risk to all missions.