In addition to fuel the expenditure of ammunition and other consumables will reduce combat endurance, for example the limiting factors for a nuclear attack submarine are its torpedoes or for a nuclear aircraft carrier aviation fuel and aircraft munitions.
Military units will have a combat endurance, how long they can stay in the field for, measured by how long its logistics train can keep its component subunits supplied with food, fuel, ammunition and spare parts etc.
The United States Department of Defense and NATO define endurance as "the time an aircraft can continue flying, or a ground vehicle or ship can continue operating, under specified conditions, e.g., without refueling.
The improvements of combat endurance are largely concerned with better efficiency to the current platforms and they aim to bridge the gap between the resources available today and the future.
There are three improvement categories focused on this area: The U.S. Department of Defense identified three breakthrough technologies that could significantly improve its capabilities and combat endurance and these are: 1) blended wing body for fixed-wing, heavy-lift aircraft; 2) variable speed tilt rotor for vertical lift aircraft; and, 3) blast bucket design concept for light armor ground vehicles.