The Japan Maritime Self-Defense Force (JMSDF) Izumo-class helicopter carrier JS Izumo (DDH-183) has appeared in public view with a dramatically redesigned bow, marking a key milestone in its conversion to operate F-35B short takeoff and vertical landing (STOVL) fighter jets.
The lead ship of the class was recently sighted alongside the quay at Japan Marine United’s (JMU) Isogo shipyard in Yokohama City, south of Tokyo, where it has been undergoing the second phase of its modification program. According to observers, the vessel left dry dock around April 17, revealing a newly reshaped forward flight deck with a rectangular bow—representing a significant departure from its original tapered design.
Originally, Izumo featured a trapezoidal bow that narrowed toward the front. The new configuration introduces right-angled edges, creating a rectangular layout.
According to the JMSDF, this modification is intended to suppress airflow turbulence around the bow and improve the safety of F-35B flight operations. To achieve this, the flight deck has been extended laterally, eliminating the narrow forward section and enabling more stable takeoff and landing conditions for STOVL aircraft.
The two Izumo-class ships are undergoing two rounds of modification, taking advantage of their periodic refit and overhaul cycles, which occur approximately every five years separately.
The latest modification represents the second phase of JS Izumo’s conversion. The first phase, completed in June 2021 at the same JMU facility, included heat-resistant deck coatings to withstand the F-35B’s exhaust, installation of visual landing aids, and the addition of a centerline marking (tramline) along the flight deck.
The second phase began when JS Izumo entered dry dock on November 1, 2024. This stage involves more extensive structural modifications, including the bow redesign. The full conversion is expected to be completed by the end of Japan’s fiscal year 2027 (March 2028).
Parallel Work on sistership JS Kaga
Work on the second ship of the class, JS Kaga, has followed a similar path. Its first phase of modification began in late fiscal year 2021 at JMU’s Kure shipyard in Hiroshima Prefecture. The Kaga emerged from dry dock in April 2023 with its bow already converted to a rectangular configuration, becoming the first Izumo-class vessel to display the new design.
The second phase of JS Kaga’s modification is scheduled to begin in the current fiscal year 2026, with completion expected by the end of fiscal year 2028 (March 2029).
From Helicopter Destroyer to Light Carrier
The Izumo-class was originally designed to operate multiple helicopters from a full-length flight deck and has long been categorized by reference works such as Jane’s Fighting Ships as a helicopter carrier.
With the integration of fixed-wing F-35B operations, the ships are effectively transitioning into light aircraft carriers. However, the Japanese government continues to avoid the term “aircraft carrier” due to longstanding political and constitutional sensitivities, instead describing them as “multi-purpose operation destroyers.”
New “CVM” Designation
Reflecting these major modifications, Japan’s Ministry of Defense updated its classification standards for naval vessels in October 2024, introducing a new hull designation: CVM.
According to the JMSDF, CVM stands for Cruiser Voler Multipurpose, referring to an “aircraft-carrying multi-role escort vessel.” Officials emphasize that the designation does not imply a conventional aircraft carrier and is not derived from the U.S. Navy’s “CV” classification.
For now, both JS Izumo and JS Kaga retain their DDH (helicopter destroyer) designation, with the transition to CVM expected after their modifications are complete.
Strategic Implications
The conversion of the Izumo-class marks a significant evolution in Japan’s maritime capabilities, enabling the JMSDF to operate fifth-generation aircraft at sea for the first time since World War II.
While officially framed as a defensive measure, the program enhances Japan’s ability to project air power in the Indo-Pacific and reflects a broader shift toward more flexible and expeditionary naval operations.