 During World War I, the rangekeepers could generate the necessary angles automatically, but sailors had to manually follow the directions of the rangekeepers (a task called "pointer following" or "follow the pointer").Pointer following could be accurate, but the crews tended to make inadvertent errors when they became fatigued during extended battles.During World War II, servomechanisms (called "power drives" in the U.S. Navy and RPC in the Royal Navy) were developed that allowed the guns to automatically steer to the rangekeeper's commands with no manual intervention.