JS Kaga of the Japan Maritime Self-Defense Force Begins F-35B Training on June 4, Demonstrating Japan-U.S. Maritime Air Power

The F-35B of the U.S. Marine Corps lands again on the flight deck of the Kaga. The Japan Maritime Staff Office announced on May 28 that the Japan-U.S. joint training will take place from June 4 to 12 in the western Pacific, with the participating units being the JS Kaga (DDH-184) of the Japan Maritime Self-Defense Force and the U.S. Marine Corps F-35B. The training item is straightforward: "Deck Landing and Take-off Training," which refers to training for take-offs and landings on the deck.

This single line carries more weight than it appears.

Kaga Approaches Operational Capability from Testing

JS Kaga is the second ship of the Izumo-class destroyers, measuring approximately 248 meters in length, and has been treated as a helicopter carrier by the Japan Maritime Self-Defense Force. However, due to changes in the bow shape, heat-resistant deck, and the establishment of aviation-related facilities, it is gradually accepting the operation of the F-35B, a short takeoff and vertical landing aircraft. The tests off the U.S. West Coast in 2024 were primarily aimed at confirming the compatibility of the hull and aircraft. This training in the western Pacific is closer to a real operational environment.

For the U.S. Marine Corps, this is not merely a goodwill training exercise. The F-35B is equipment that can verify whether allied decks can be used as temporary air bases, not just on amphibious assault ships. The acceptance of U.S. Marine Corps aircraft by Japan's ships means that the air power of the Japan-U.S. alliance will be less constrained by fixed bases.

Chinese Aircraft Carrier Activities and the Same Maritime Sense

The timing cannot be overlooked. According to Japan's Joint Staff Office, the Chinese Navy's aircraft carrier Liaoning conducted repeated take-offs and landings of carrier-based fighters and helicopters in the Pacific southwest of Okinotorishima and south of Miyakojima from May 26 to 28. Reports from Jiji Press indicate that approximately 170 take-offs and landings were confirmed over the three days. While it is dangerous to conclude the wartime capabilities of the Chinese carrier group based solely on this number, it is hard to deny that the training density is increasing.

During the Cold War, the Japan Maritime Self-Defense Force closely monitored how Soviet submarines passed through the Soya, Tsugaru, and Tsushima Straits. The current focus is on the Philippine Sea, which spreads outside the southwestern islands. Aircraft carriers, patrol aircraft, unmanned aerial vehicles, and anti-ship missiles are beginning to overlap in the same operational space. The F-35B training on Kaga should be understood within this new maritime sense.

Capabilities Still Limited

Here, we want to avoid overestimating. Kaga will not become a regular aircraft carrier of the U.S. Navy. The operation of the F-35B from a flat deck without a ski jump is constrained by factors such as onboard fuel, armament load, wind direction, deck temperature, and maintenance space. It will take time for Japan's planned F-35B unit to mature as a carrier-based air wing. The Japan Maritime Self-Defense Force has been an organization centered on anti-submarine warfare using destroyers, submarines, and patrol aircraft, and there has been almost no culture of operating fixed-wing carrier-based aircraft since the post-war period.

Nevertheless, limited capabilities are not meaningless. In the event of a crisis around the southwestern islands, runways at bases such as Naha, Chikushino, Nittahara, and Iwakuni may not always be available. The mere option of temporarily launching the F-35B to sea or pushing it forward complicates the opponent's attack plans. Deterrence often involves creating margins in the opponent's calculations.

Practical Challenges of the Japan-U.S. Alliance

What I focus on in this training is not the glamorous take-off and landing footage, but rather the details of maintenance, supply, communication, and air traffic control. The management of F-35B data, armament loading, heat management on the deck, night operations, and firefighting and rescue in case of accidents. How well these align between U.S. Marine Corps procedures and the Japan Maritime Self-Defense Force's onboard regulations will determine the practical value.

In late June, Resolute Dragon 26 and Valiant Shield 2026 are also scheduled. According to the announcement from the Joint Staff Office, Valiant Shield will take place from June 22 to July 1 over a wide area including Japan, Guam, and around Hawaii. USNI News has also mentioned information about the deployment of the Typhoon missile system and HIMARS within Japan, along with Resolute Dragon 26 involving the Ground Self-Defense Force and U.S. Marine Corps. In other words, the F-35B training on Kaga should be seen as a prelude to a series of dispersed operational training extending from the first island chain to the second island chain, rather than an isolated maritime event.

More Important Questions than Aircraft Carrier Conversion

Domestically, the term "aircraft carrier conversion" is often used. However, this term is somewhat coarse. The significance of Kaga cannot be measured solely by whether or not it possesses an attack aircraft carrier. A more practical question is how far Japan and the U.S. can share the same deck, the same communication network, and the same supply plans.

The true weakness does not lie in the size of the ship. It is in the speed at which political approval for take-offs and landings can be granted, the ability to continue training in the event of an accident, and the willingness to establish a support network that includes ports and civilian airports from peacetime. Each time Kaga accepts an F-35B, Japan is not moving closer to being a "country with an aircraft carrier," but rather being questioned whether it can truly operate a "defense that does not rely on fixed bases."

Sources

• Japan Maritime Staff Office, Japan-U.S. Bilateral Exercise, May 28, 2026
• USNI News, Western Pacific Pulse, May 29, 2026
• Japan Joint Staff Office, Participation in Valiant Shield 2026, May 22, 2026
• Nippon.com/Jiji Press, China Conducts 170 Aircraft Takeoffs, Landings on Flattop in Pacific, June 2, 2026