Japan:
Hiyō-class aircraft carrier
Jun'yō (Peregrine Falcon) at Sasebo, Japan, September 1945.
Jun'yō was converted from the fast passenger liner
Kashiwara Maru during construction, and was completed in 1942.
Two HA-201 class submarines are visible alongside. These were similar in many ways to German Type XXI and Type XXIII submarines.
Jun’yō and
Hiyō were unusual carriers, but they weren't escort carriers.
These two ships were converted from large ocean liners like many escort carriers, especially Japanese. This alone says nothing as many light carriers were also converted from other ships along with a handful of fleet carriers (most never completed or completed immediately after the Washington Naval Treaty). This was part of a more general program to bulk up Japanese carrier forces by converting as many ships as possible due to the limitations of their shipyard capacity..
Despite being converted from liners like the smaller
Taiyō (CVE)，the ships were large enough to have a good sized flight deck, hangar and aircraft capacity similar to other medium fleet carriers like
Hiryū or
Illustrious. This was initially slated as 48 ready A6Ms，D3As，and B5Ns but varied as the war went on due to aircraft availability. Escort carriers generally had 20-30 depending on design.
Operationally these two ships were always deployed with other fleet or light carriers. They spent much of the war in the 2nd Carrier Division of the Third Fleet with
Shōkaku and
Zuikaku the core of the 1st CarDiv.
Hiyō sank during the Battle of the Philippine Sea operating with her sister the three other operational Japanese fleet carriers and the four operational light carriers. No escort carriers were in this operation, their missions were generally aircraft ferry and occasionally convoy escort and during the war they were mostly attached to the Combined Fleet directly or from late 1943/early 1944 to General Escort Command.
The main drawback of these two ships was the very slow speed for fleet carriers. Typical speeds were 30-33 knots while these ships were rated for 25 and with wartime loads never broke 23 in service. This is better than most escort carriers (15-21 knots)，but still severely limited the capability of the aircraft launching from the ships (in short more wind over deck means a shorter takeoff run for the same payload. Since aircraft operations required spotting aircraft on the rear of the flight deck for large launch groups, a longer takeoff run means you have less room to spot aircraft as the first ones must get airborne).
These were unquestionably the weakest fleet carriers Japan operated
