The was a class of four destroyers of the Imperial Japanese Navy. According to most sources, they are regarded as a sub-class of the , partly because the Imperial Japanese Navy itself kept the improvements made a secret, and did not officially designate these four destroyers as a separate class. Background After a number of years of operational experience with the Fubuki class, the Imperial Japanese Navy General Staff issued requirements for four additional destroyers, with a maximum speed of , range of at , and armed with Type 8 torpedoes. These destroyers were intended to operate with the new series of fast and powerful cruisers also under consideration as part of a program intended to give the Imperial Japanese Navy a qualitative edge with the world's most modern ships. The new vessels were built from 1931-1933. Design The main difference in design between the Akatsuki vessels and the standard Fubuki-class was the use of a new high-pressure boiler, which enabled the number of boilers to be reduced from four to three without a reduction in power. This also enabled the fore smokestack to be made narrower than on standard Fubuki-class vessels, and this feature was the most evident visual recognition feature between the two designs. Other improvements over the Fubuki class included a larger bridge structure, with the addition of another level to house improved fire control facilities, and a splinter-proof torpedo launcher/turret, which allowed the torpedo launcher tubes to be reloaded in action. The four ships incorporated many weight-saving measures, and was the first all-welded Japanese ship. However, the Akatsuki class shared a number of inherent design problems with the Fubuki class. The large amount of armament combined with a smaller hull displacement than in the original design created issues with stability. After the Tomozuru Incident, in which the basic design of many Japanese warships was called into question, additional ballast had to be added. In the Fourth Fleet Incident, during which a typhoon damaged virtually every ship in the Fourth Fleet, issues with the longitudinal strength of the Akatsuki-class hull was discovered. As a result, all vessels were reconstructed from 1935-1937. An additional 40 tons of ballast was added, the bridge reduced in size and the height of the smoke stacks was decreased. The number of torpedo reloads were reduced from nine to three (for the center launcher only), and fewer shells were stored for the guns.