Japan is embarking on rebuilding its carrier fleet, a feat not undertaken since the end of World War II. This project involves significant modifications to its Izumo-class “helicopter destroyers,” transforming them into F-35B light carriers, a development that is rapidly gaining momentum. 

This month, Naval News reported that the Japan Maritime Self-Defense Force (JMSDF) had completed the first two-stage modification for its helicopter destroyer JS Kaga to operate the Lockheed Martin F-35B fighter aircraft. Naval News says the first modification was done with a regular inspection for about two years, starting at the end of fiscal year 2021. The publication then adds that the second special modification of Izumo, which will begin this fiscal year, will reflect the results of those tests. 

Naval News notes that the JMSDF will continue to advance the necessary modifications to acquire the operational capability of the F-35B on Izumo-class destroyers.

The meticulous planning of the modifications to two Izumo-class helicopter destroyers, JS Izumo and JS Kaga, underscores the JMSDF’s strategic foresight and capability. These modifications are strategically underway in two main stages, demonstrating the precision of the JMSDF’s timing, which coincides with the vessels’ periodic refit and overhaul programs, which occur every five years. Both ships are projected to complete their conversion to F-35B light carriers around the fiscal year 2027, further instilling confidence in the JMSDF’s strategic planning and capabilities. 

Naval News reports that the JMSDF has already begun the conversion of JS Izumo into a carrier capable of supporting F-35B operations in Yokohama City of Kanagawa in the first half of 2020. It further states that the second refurbishment of Izumo will commence in the fiscal year 2024, with the Japan Ministry of Defense expecting the modifications to be completed by the end of the fiscal year 2026. This ongoing progress builds anticipation for the future capabilities of the JMSDF.

The decision to convert the Izumo-class helicopter destroyers into light carriers has been marked by controversy. Critics point out that it goes against Japan’s longstanding pacifist foreign policy. However, other criticisms of Japan’s decision to rearm with light carriers come from a military perspective. 

In an October 2021 article in the peer-reviewed Asian Security Journal, Brendon Cannon and Ash Rossiter argue that while the conversion of the JS Izumo and JS Kaga helicopter destroyers into light carriers provides tangible military benefits, such as enhancing Japan’s territorial defense capabilities, those benefits do not fully justify the decision to convert the ships. 

Cannon and Rossiter point out from a military standpoint that China’s and North Korea’s increasingly capable anti-access/area-denial capabilities (A2/AD) make carriers especially vulnerable. They add that Japan does not have sufficient screening and logistics ships to support carrier operations and that the daunting infrastructure, technology, knowledge requirements and systems integration challenges mean that, in the near term, Japan will not have independent carrier warfare capabilities.

However, Cannon and Rossiter suggest a more optimistic perspective. They propose that it may be more feasible for Japan to operate light carriers within a larger US-led coalition. 

In line with that perspective, Japan’s light carriers can address a looming US “carrier gap” that could leave it with insufficient carriers for effective operations. This potential for collaboration and shared defense responsibilities could enhance Japan’s military capabilities and strategic position.

In a March 2024 Defense One article, Bryan McGrath argues that delaying the next Gerald R. Ford supercarrier to 2029 would further undermine the US naval shipbuilding base, result in losses of hard-to-replace skilled manpower and impact the US nuclear submarine industrial base, as both share critical technologies such as nuclear propulsion. 

McGrath points out that long production gaps will shrink the US Navy’s 11 already-overstretched carriers, noting the definite lifespan of their nuclear cores, and that the US Navy can only keep two out of an ideal three carriers forward-deployed indefinitely.

Given that, multinational naval exercises involving the US and Japan’s JS Izumo and JS Kaga may offer a glimpse of the role of Japan’s light carriers in a coalition setting. 

However, in an October 2021 War on the Rocks article, John Bradford and Olli Pekka Suorsa note that light carriers are unlikely to change the anticipated outcomes of combat scenarios envisioned in the Korean Peninsula, Senkaku Islands, the Taiwan Strait, and the South China Sea.

Bradford and Suorsa note that light carriers are still costly assets vulnerable to increasingly capable anti-ship missiles and submarines. They point out that it is improbable that they will alter the distribution of naval supremacy, which influences deterrence calculations. They also say light carriers offer marginal benefits over long-range land-based aircraft and more distributed basing options. 

Bradford and Suorsa also say that if Japan gets involved in a South China Sea conflict, its light carriers may be exposed to unnecessary risk if they encounter China’s A2/AD capabilities. 

While there may be solid arguments for and against the military value of Japan’s light carriers, Cannon and Rossiter say that their real value may be in their symbolic value, which serves strategic and political ends to boost Japan’s credibility in the Pacific and with the US. 

In an April 2022 Naval News article, Yoshihiro Inaba notes that JS Kaga’s conversion is believed to be aimed at strengthening Japan’s Indo-Pacific presence during Indo-Pacific Deployments (IPD), which are long-term deployment of the Izumo-class ships and other ships in the region that has been ongoing for several years. 

As the F-35B is the main asset of Japan’s light carriers, and the country is one of the largest F-35 operators, the type could enhance interoperability with US and allied forces and facilitate further technology transfer between Japan, the US and its other key allies.

The F-35B could also be a focal point of Japan’s participation in AUKUS Pillar II, which focuses on advanced technologies, in contrast to AUKUS Pillar I, which focuses on acquiring nuclear attack submarines (SSN) for Australia. 

Breaking Defense noted this month that AUKUS is considering cooperation with Japan on AUKUS Pillar II advanced capability projects while making it clear that actual AUKUS membership for Japan is off the table.

Such projects under AUKUS Pillar II include AI, quantum computing, undersea drones, hypersonic missiles and electronic warfare technologies. Japan’s F-35Bs may benefit from advancements in AI for sensor fusion and electronic warfare technology for radar warning, targeting support, and self-defense.