On November 6, the Japan Maritime Self-Defense Force announced the completion of tests integrating the F-35B Joint Strike Fighter with Japan’s recently modified destroyer JS Kaga. Speaking at a joint Japan-US press conference on the destroyer’s flight deck, Japanese Vice Admiral Goka Yoshihiro said that Kaga’s certification process marked an unprecedented strengthening of relations with the US Navy. Tokyo has been motivated to bolster Japan Self-Defense Force (JSDF) capabilities by concerns about China’s military modernization and perceived threats to Japanese territory. JS Kaga’s completion of the F-35B development test is a significant milestone on Japan’s path toward interoperability and resilience in combined operations with the United States and its allies.
In 2019, Japan announced it would purchase 42 F-35Bs from the United States. The F-35B is the short take-off/vertical landing (STOVL) Joint Strike Fighter variant designed for ships that lack the fixed-wing launch and recovery systems found on aircraft carriers. The Japan Maritime Self-Defense Force has modified the flight decks of two helicopter destroyers, JS Izumo and JS Kaga, to withstand the heat of the F-35B’s powerful engines and enable day and night operations. Japan’s sea trials with the fifth-generation fighter began in 2021, leading up to recent US Navy F-35B landings on Kaga to test operations in waters off San Diego.
Benefits of Short Take-Off/Vertical Landing
The acquisition of STOVL capability will greatly improve the flexibility of JSDF fighter operations. Aside from being able to take off and land on ships without catapults and arresting wires, F-35Bs can operate from short and austere airstrips. Japan’s mountainous terrain and urban development have resulted in relatively few airfields suitable for conventional fighter jets, which typically require runways that are 2,000 meters or longer. STOVL aircraft, in contrast, can take off from runways only several hundred meters long, ensuring greater redundancy if some airfields are damaged or destroyed in wartime.
F-35Bs are also equipped with advanced technologies that could enhance Japan’s deterrence of China and other regional rivals. The fighter’s stealth capabilities can pose dilemmas for adversaries’ intelligence, surveillance, and reconnaissance systems, generating uncertainty about F-35B positions and loadouts. The aircraft’s cutting-edge radar and sensors will elevate Japan’s tactical intelligence and situational awareness of airspace in critical contested areas, such as the East China Sea. The F-35B also has non-kinetic offensive capabilities like electronic warfare systems that can be used to degrade enemy radar and communication networks.
Ally and Partner Cooperation
The JSDF’s future employment of F-35Bs promises to improve interoperability and resilience in combined operations with the United States. The use of a common fighter and modifications to make Izumo-class destroyers more closely resemble US Navy amphibious assault ships will facilitate cross-deck landings between US and Japanese large-deck ships. This may improve the two countries’ ability to conduct distributed maritime operations that increase force survivability and expand operational reach.
The US Marine Corps has been instrumental in helping the JSDF build F-35B capability. With its decade of experience operating Lightning II aircraft, the Marines can continue to offer guidance to Japanese pilots. The 31st Marine Expeditionary Unit already has two F-35B squadrons based in the western Japanese city of Iwakuni.
While working closely with the US, the JDSF is also looking to other Joint Strike Fighter partners for support. Since 2021, Japanese military officials have engaged their British and Italian counterparts to learn about operations and best practices of Lightning II fighters. In late 2023, Japanese officers observed F-35B operations on the HMS Prince of Wales. The Royal Navy officer hosting the delegation expressed hopes to one day see a Japanese F-35B land on the British carrier. During Kaga’s recently completed development test, a British pilot landed a Royal Air Force F-35B on the ship’s deck for the first time.
Competitor reactions to Japan's F-35Bs
Japan’s effort to employ F-35Bs is one among a series of recent defense initiatives that have drawn attention and criticism from the country’s potential adversaries. The three major security documents released by Tokyo in late 2022 spelled out plans to increase the country’s defense budget and develop “counterstrike” capabilities for attacks against enemy bases. While North Korea and Russia have voiced their concerns, the most outspoken critic has been China. Beijing has repeatedly raised the alarm that Japan is pursuing a militarist agenda.
A representative critique was published on the official website of the People’s Liberation Army soon after JS Kaga began its development test in waters off San Diego last month. The authors contended that Japan’s F-35B tests were focused on acquiring offensive capabilities that were in violation of the country’s stated self-defensive policy and were increasingly distancing the country from its “pacifist constitution.”
Such criticism of Japan’s F-35B testing fits well within China’s longstanding negative portrayals of advances in Japanese military capability, which often harken back to World War II. These narratives likely seek to aggravate divisions between Japan and countries that experienced past aggression by Japan’s former imperial forces, particularly South Korea. The success of such an approach is doubtful under the current state of warming trilateral relations between the US, Japan, and South Korea.
Next steps for Japan's Joint Strike Fighters
JS Kaga’s completion of the F-35B development test marks significant progress toward fielding Japanese carriers for future Joint Strike Fighter operations, but the JSDF has a long way to go before it can conduct these operations independently or achieve cross-decking capability with the US and other partner countries.
Tokyo expects to receive its initial set of six F-35Bs in the coming months and hopes to make JS Izumo and JS Kaga fully capable of F-35B operations by the end of fiscal year 2027. It will take time to train up the initial F-35B squadron before its pilots are ready to embark on Japanese ships and certify for blue water operations. Managing command and control relationships between embarked F-35 squadrons and their carriers, likely through the impending Japan Joint Operations Command, will be crucial for coordinating at-sea operations.
The JSDF will also have to continue to think hard about high-value unit protection, as the addition of F-35Bs will make the ships increasingly tempting targets for adversaries’ anti-ship cruise missiles. To mitigate threats to Japan’s “Lightning carriers” in future operations, the JSDF can work as a joint force, with the US, and with close partners, reinforcing the trend toward closer international collaboration with Japanese forces.
