What limits a warship's speed in reverse

What determines how fast a warship can travel in reverse?

Propeller design, shaft gearing, hull form, maneuverability, and the machinery wear the navy is willing to accept.

Propeller shape and shaft gearing determine how effectively a warship can drive astern. Reverse operation is already one of the functions considered when designing most ships' propellers. The machinery's theoretical output does not by itself establish a usable reverse speed. Driving hard astern can increase wear, while a hull optimized for forward movement and awkward manoeuvring impose further limits. A speed that might be attempted in an emergency is therefore different from one suitable for regular service.