October 25, 2026: Three years ago, Japan wanted to build two seagoing BMD (ballistic missile defense) ships and was faced with two options. The first, which Japan discarded, was a ship design that carried only the Aegis BMD radar and Aegis BMD missiles. These ships would have had only that purpose. Instead, Japan decided to build two more Maya-class destroyers with additional BMD capabilities. Japan is calling these modified destroyers ASEVs (Aegis system-equipped vessels). This is part of the Japanese effort to expand its ballistic missile defenses. Most of these will still be based on the Aegis system, which is normally installed on large (8,000 tons and up) warships. Japan has eight Aegis anti-missile system destroyers but has not placed Aegis Ashore in Japan. Local civilian opposition was too strong. Civilians do not object to Aegis-equipped ships.

Not all the Japanese Aegis destroyers are the same. There are two Maya-Class ships, two Atagos, and four Kongos. By 2030, Japan plans to have twelve Aegis-equipped warships. ASEV ships are 12,000-ton vessels, 282 meters long and 37 meters wide, armed with 128 VLS cells, each containing an anti-aircraft or BMD missile. They also carry a dozen or so cruise or anti-ship missiles. ASEV has a crew of 240 and a top speed of 58 kilometers per hour. It has an Aegis radar and fire-control system that quickly launches the right missile at detected targets. The radar is supported by ECM (Electronic Countermeasures) that detects electronic threats, and an electronic jammer that disrupts them if chaff and decoys fail. There is one five-inch gun and a helicopter flight deck with a hangar for one helicopter.

While the Japanese destroyers are smaller than the ASEV, their armament is more diverse and their capabilities more extensive, which requires larger crews, usually 300 sailors. Destroyers are faster, can travel farther from Japan, and cost more to build and operate than the ASEV. Despite that, the first two ASEVs will cost more than a destroyer because of development costs. If Japan builds more ASEVs, they will be cheaper than destroyers. The Navy would rather have more destroyers because the ASEV is more of an Aegis system platform than a traditional destroyer.

The Maya class destroyers are improved versions of the earlier Atago class. The Mayas also borrow heavily from the first four Japanese Aegis-ABM ships, the 9,500-ton Kongos, built in the 1990s and modeled on the American Burke-class Aegis destroyers. The Kongos have 90 VLS (Vertical Launch System) cells for anti-aircraft/missile missiles, as well as ASROC anti-submarine rockets that carry an anti-submarine torpedo, effectively extending the torpedo's range by 22 kilometers. Japanese Burke-type destroyers also carry a five-inch gun and eight Japanese-designed anti-ship missiles, like the American Harpoon. The Maya class has 96 VLS cells (as does Atago) and more advanced electronics that let the Mayas link with the U.S. Navy CEC (Cooperative Engagement Capability), enabling real-time sharing of sensor and other data between other CEC-equipped ships and even shore-based systems like Aegis Ashore.

The two land-based Aegis Ashore anti-missile systems were not expected to enter service until 2024, but popular opposition ended the ashore program. The ASEV was developed to do what Aegis Ashore was intended to do, but it won’t enter service until 2027 and 2028. ASEV can operate in coastal waters, harbors, and on the high seas to protect the fleet. ASEV is a more flexible but more expensive substitute, at $2.6 billion each, than the $1.6 billion Aegis Ashore now operational in Romania and Poland.

Japan’s eight destroyers armed with Aegis anti-missile systems (four Kongos, two Atagos, and two Mayas) and the proposed two ASEVs will give Japan ten Aegis systems, all operating from ships. North Korea continues to be a threat, and how much more of a ballistic missile threat China becomes is still considered less of a problem now but could escalate in the future. China has a long history of threatening but not acting. North Korea has demonstrated an ability to attack without warning and did so in 2010. North Korea has always been less cooperative than China, though China remains a threat.

Japan's 2017 decision that it didn't need the more expensive THAAD anti-missile system prompted the original Aegis Ashore concept, after realizing two land-based Aegis systems on the main island could do the same job more cheaply. That, plus Aegis-equipped destroyers armed with the SM-3A anti-missile missile, would let those two land-based Aegis systems protect all three home islands. Local civilians protested because the missile launches were noisy and the Aegis radar generated a lot of microwave radiation. This forced government officials to oppose the Aegis Ashore, and Japan lost the cost savings of a land-based system. The expensive ASEV was developed to replace Aegis Ashore.

James F. Dunnigan