: Japans DDH-X, the successor to the Haruna and Shirane-class helicopter carrying destroyers, is not exactly a destroyer. Its called a destroyer, and is ostensibly designed to carry a similar air complement (three SH-60s and one MH-53 helicopters). However, one look at the artists impressions available, and one could wonder if Japan is trying to sneak a new carrier into service by calling it a destroyer. The new design will displace roughly 13,500 tons, or about the size of a World War II Independence-class light carrier (built on the hull of a light cruiser).

The impressions show a flat-decked ship with an island to the starboard side. SH-60s are seen, but such a ship could conceivably also carry V/STOL fighters such as the Yak-38, AV-8/AV-8B, or the V/STOL version of the F-35. The Dedalo, a former Independence-class carrier that served until 1989, had an air group of four Harriers and eight helicopters. The new Japanese DDH looks like a carrier, and the mission sounds like that of a carrier. That makes the designation of helicopter carrying destroyer a useful fiction.

Useful fictions are nothing new for Japan. In its older incarnation as the Imperial Japanese Navy, there were numerous instances of these involving surface units. The most glaring were the heavy cruisers of the Mogami-class. Supposedly light cruisers displacing 8,500 tons (and fifteen six inch guns), these were really heavy cruisers of over 13,000 tons (with ten eight-inch guns). The claims that those ships were compliant with naval arms limitation treaties were on the disingenuous side.

Another instance involved the super-battleships Yamato and Musashi. The guns had been called special 40-centimeter, leading many Allied intelligence officers to believe the vessels used sixteen-inch guns. As it is known now, the main battery consisted of nine eighteen-inch guns. 

More recently, the Osumi-class landing ships were designated as landing ship tanks (LSTs), when in reality, they could operate as helicopter assault ships (they carry two air-cushioned landing craft and can land two CH-47s) and also look a lot like carriers. Harold C. Hutchison

Links to images:

New DDH projections:
http://www.ships-net.co.jp/detl/200107/091l.jpg

Osumi-class LST:
http://www.globalsecurity.org/military/world/japan/images/osumi09_h.jpg