Two Tone class cruisers were originally envisaged as the fifth and sixth vessels in the Mogami class,
however, by the time construction began, weaknesses in the Mogami class design had become clear,
and Japan no longer had any intention of even pretending to abide by the limitations of the London Naval Treaty.
This resulted in a new design, which turned out to be quite different from the Mogami class,
although external dimensions were very similar. Unique to the ships was the
placement of their main armaments forward of the bridge, which left their
quarter decks free for aircraft usage. The Tone class cruisers were intended to provide
long-range air scouting for cruiser squadrons and to operate together with
aircraft carrier task forces. Commissioned in 1938-1939 these ships became the last heavy
cruisers produced for the Imperial Japanese Navy.

Tone and Chikuma operated together for almost all of their careers as consorts for aircraft carriers. The ships were part of the covering force
during the attack on Pearl Harbor, the second Battle of Wake Island, operations in the Netherlands East Indies, the Indian Ocean raids,
the battles of the Eastern Solomons, Santa Cruz, Philippine Sea and Leyte Gulf.

Both Tone class cruisers took part in the Battle of Midway as a Cruiser Division 8 alloted to First Air Fleet (First Mobile Force).