The Japanese Navy's Strategic Review of 1959-61 completely reformulated the Navy's thoughts on major surface combatant design. The complete helplessness of the Yamato class battleships when facing high-altitude nuclear-armed bombers was a stark lesson that the day of these ships was done. For all the impressive performance of their 18 inch guns and the provision of nuclear shells for those guns, they were incapable of matching the firepower of missile-armed ships. In addition, they were extraordinarily expensive to operate and a drain on badly-needed manpower. They had to go.
In addition, the old Nachi class cruisers were urgently in need of replacement and the only-slightly-less-obsolete Atagos were not far behind. The Strategic Review proposed a new class of eight large, missile-armed cruisers that would replace both the Yamato class battleships and the Nachi class cruisers. These 22,500 ton ships carried as their primary armament a battery of sixteen long-range nuclear-tipped anti-ship missiles in an array of fixed launch tubes forward. The Kawachi class were not designed for sustained combat; unlike the contemporary Indian Mysore class they did not carry reloads for their missile tubes. The Kawachis were designed to launch a single overwhelming blow against a maritime target. Doctrine for the new cruisers envisaged them operating in divisions of four ships, firing all 64 missiles in a coordinated salvo. The missiles themselves were designated the Kabuto and were supersonic weapons, having a speed of Mach 1.8 and a range of over 300 nautical miles. The ships also had a typical four-barrelled Nodachi anti-aircraft missile launcher aft that gave it the capability to engage B-52 and B-58 class aircraft - in theory at least. Finally, the ships were armed with six of the new Type 21 3 inch L80 anti-aircraft gun in three twin turrets, two amidships, one forward.
Two radical features distinguished the Kawachi class from previous Japanese battleships and cruisers. One was that the new ships were completely unarmored. In a nuclear exchange, armor plating was regarded as being of little value but greatly increased the cost and construction time of the ships. Secondly, the Kawachi class were gas turbine powered. This was also a reflection of the nuclear environment; in the event of an emergency the ships could get underway at a few minutes notice.
The first group of eight Kawachi class cruisers were ordered in 1961 to replace the Yamatos and the Nachi class. The first pair, Kawachi and Settsu, had just been delivered when the Showa Restoration Coup took place. They were in Yokohama shipyard when the campaign of assassinations that marked the start of the Showa Restoration Coup took place. Both ships broke out and headed for Taiwan but came under heavy attack from military forces supporting the Showa Coup. Settsu was sunk by air and submarine attack while Kawachi was severely damaged and eventually sank in the approaches of Kaohsiung port. She was later raised and repaired, serving first as the flagship of the Taiwanese fleet, then as a training ship before being scrapped in 2002.
The remaining six ships were completed at a slow rate, the last (Tokiwa) being delivered in 1971. A year later, at the Pescadores Incident, Yashima was reduced to a wreck by the rapid-firing guns on Indian destroyers and, although she returned to port, was written off as a constructive total loss and scrapped. The remaining five ships remained in Japanese service but saw little additional action and spent most of their lives in Kagoshima Bay. They were scrapped between 1991 and 1997.
Four more Kawachi class ships had been ordered in 1962 to replace the Atago class cruisers but they were never laid down and were cancelled in the aftermath of the Showa Restoration Coup. The leadership installed in Japan by that coup saw little use for a large fleet of surface ships and made a policy decision that the Japanese Navy would, in future, concentrate on the operation of submarines carrying cruise and ballistic missiles and the hunter-killers needed to protect them. The Navy also operated long range bombers and air defense fighters but its surface fleet fell into progressive disrepair. Throughout the late 1960s and 1970s the ships were sent to the breakers and, by the mid-1980s, the surface fleet consisted of a few aged and ill-maintained cruisers and destroyers supported by a large mosquito fleet of torpedo- and missile-armed fast attack craft.