Warship availability depends on numbers and operating stress

The arrival of HMS Ocean after Hermes left service illustrates the practical value of maintaining four major ships. As with four ballistic-missile submarines, that number can support one vessel at sea and another available for operations while the remainder train or undergo maintenance. Aircraft carriers combine many systems exposed to salt water, high speed, sharp maneuvering, weapons firing, and repeated aircraft launches and recoveries. Those demands wear a ship differently from steady commercial service, so software models based on merchant operations may not predict warship performance accurately. CAM ships, MAC ships, and most escort carriers did not experience the full operating cycle expected of fleet carriers, even when a few faced severe action. The closest comparisons included escort-carrier operations off Italy under Philip Vian with HMS Unicorn and later Pacific bombardment support, yet those ships were still not meant to absorb every demand placed on a fleet carrier. Availability depends on both hull numbers and the distinctive stresses imposed by naval operations.