Kaga to Train with F-35B in June: Practical Issues of the JMSDF's 42-Aircraft System Emerge

The seemingly mundane schedule of a port call to Iwakuni is bringing the Japan Maritime Self-Defense Force's (JMSDF) air operations closer to reality. According to a report by USNI News on May 20, the destroyer "Kaga" (DDH-184) will dock at the U.S. Marine Corps Iwakuni Air Station from June 1 to 4, equipped with the necessary gear for operating the U.S. Marine Corps F-35B. F-35B flight operations training is expected to take place aboard "Kaga" later in June.

What is noteworthy here is not the F-35B itself, but the fact that the processes of equipment loading, port adjustments, local explanations, and procedural confirmations with the U.S. Marine Corps have begun to move as a single flow. The ability to launch and recover carrier-based aircraft cannot be established solely by the heat-resistant coating of the deck or the shape of the bow. Rather, it is determined by the accumulation of mundane items such as maintenance equipment, fuel, ammunition safety, control, weather judgment, and noise management.

Kaga's Training Shifts from Testing to Operational Preparation

"Kaga" has already conducted F-35B-related tests in the U.S. in the fall of 2024 and accepted F-35B operations from the British aircraft carrier "Prince of Wales" in August 2025. Furthermore, training involving U.S. Marine Corps F-35B is said to have been conducted during the annual exercises in October 2025. This port call to Iwakuni is an extension of that, but its nature is somewhat different.

Past tests were heavily focused on confirming whether "this ship can launch aircraft." The training in June is closer to the stage of confirming "how to connect the operations of domestic bases, local governments, the U.S. Marine Corps, and JMSDF vessels." It is noteworthy that the Iwakuni City Council has requested the Chugoku-Shikoku Defense Bureau to alleviate residents' concerns and impacts on their lives, and has asked that Iwakuni not be designated as a regular port or home port for vessels.

The capability of carrier-based aviation is measured not only by the number of launches and recoveries at sea but also by how much the land side can accept repeated training.

42 F-35Bs and Two Command Structures

Japan plans to ultimately possess 42 F-35Bs. According to USNI News, the first three were delivered last year, and another three arrived this year. Training has begun at the Air Self-Defense Force Nittahara Base with support from U.S. Marine Corps pilots.

However, there is a structural issue here. The F-35B is an Air Self-Defense Force aircraft, while the operating deck is on the JMSDF's "Izumo" class destroyer. The education of fixed-wing aircraft crew members, onboard control, deck operations, maintenance supply, and responsibility sharing in the event of an aviation accident are difficult to manage with just a peacetime organizational chart. The JMSDF has aviation units such as the P-1 patrol aircraft and SH-60K, but the experience of continuously operating short takeoff and vertical landing aircraft from destroyers is a different matter.

In my view, the immediate focus is not on how many F-35Bs "Kaga" can carry. Rather, it is about how frequently training can be conducted with Air Self-Defense Force aircraft on JMSDF vessels, with technical support from the U.S. Marine Corps. If it is just a few symbolic launches and recoveries a year, there may be political effects. However, if we consider a contingency around the Nansei Islands, it is necessary to refine operational procedures under conditions such as nighttime, bad weather, damaged decks, and communication interference.

Renovation Schedule and the Significance of RIMPAC 2026

"Izumo" is currently undergoing the final modifications of the second phase in Yokohama, expected to be completed by March 2028. "Kaga" is also set to enter the second phase of renovations within the next few months, with completion scheduled for March 2029. This means there will be a gap of several years before the JMSDF can fully utilize two F-35B-capable ships.

On the other hand, "Kaga" is expected to operate as part of the second surface force for the Indo-Pacific deployment 2026, alongside the destroyer "Fuyuzuki" (DD-118) and the supply ship "Mashu" (AOE-425), and participate in RIMPAC 2026, which will take place around Hawaii from June 24 to July 31. This is not merely a matter of international goodwill. The overlap of F-35B training, supply ship accompaniment, and participation in exercises hosted by the U.S. Third Fleet will allow "Kaga" to link small carrier-like air operations and long-range deployment in a single voyage.

Utility and Limitations for the Defense of the Nansei Islands

If "Kaga" and "Izumo" can operate the F-35B, they could serve as alternative launch and recovery points in the event of an attack on air bases in the Nansei Islands. This is a clear advantage for Japan's defense plan, as it allows for some supplementation of air operations that depend on fixed runways with a mobile deck at sea.

However, we should avoid overestimating this capability. The "Izumo" class is not a large aircraft carrier of the U.S. Navy and has limitations in terms of the number of aircraft it can carry, ammunition capacity, maintenance areas, and fleet air defense capabilities. Even if the Chinese side views this capability as a threat, whether Japan can utilize it as a sustainable strike force is another matter. Without integrated operations involving escort fleets, supply ships, P-1 patrol aircraft, E-2D, ground air defense, and U.S. military bases, F-35B-equipped ships cannot sustain combat for long on their own.

That is why the port call to Iwakuni is not a small piece of news. The time required for resident explanations, the loading of U.S. Marine Corps equipment, and the adjustment of training areas are the cumbersome procedures that form the foundation of practical air operations. The true challenge lies not in capturing the F-35B on the deck in a photograph, but in how many times we can repeat the logistics and local government adjustments behind that photograph.