The first ships were designed around the time of the Vietnam War, and certain aspects of the design were influenced by operations there. To a certain extent, the carrier operations in Vietnam demonstrated the need for increased capabilities of aircraft carriers over their survivability, as they were used to send sorties into the war and were therefore less subject to attack. As a result of this experience, "Nimitz"-class carriers were designed with larger stores of aviation fuel and larger magazines in relation to previous carriers, although this was partly as a result of increased space available by the new design of the ships' propulsion systems.