Japanese light cruisers evolved from scouts into destroyer leaders

Early Japanese protected cruisers scouted for the battle fleet, but later light cruisers increasingly served as destroyer-squadron flagships. The 3,500-ton designs proved too small, leading to the long 5,500-ton series even as British Hawkins and American Omaha types demonstrated the value of larger scouts. Washington redirected competition toward the 10,000-ton ceiling, while London divided available tonnage by gun size and forced careful replacement arithmetic. The Mogami class began with 6.1-inch guns before conversion to heavy cruisers, and the Tone class was completed directly in that heavier form, showing how treaty rules shaped nominal categories as much as operational need.