Japanese destroyers of World War II included some of the most formidable destroyers (駆逐艦, kuchikukan) of their day. This came as a nasty surprise to the Allies, who had generally underestimated Japanese technical capabilities. The Japanese had reassessed their naval needs in the mid-1920s and, placing an emphasis on ship and weapons technology and night fighting expertise, developed a completely new destroyer design. Subsequent development from one destroyer class to the next was not, however, a smooth progression. Aside from the usual changes arising from experience, serious design faults also came to light and naval treaties imposed restrictions. As a result, the early "Special Type" destroyers required significant changes and the specifications of subsequent classes was reduced in one