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In a significant move to bolster its national defense capabilities, Japan’s Ministry of Defense (MoD) has signed contracts to construct two state-of-the-art Aegis System Equipped Vessels (ASEVs). The vessels, designed to enhance Japan’s maritime defense, will be crucial to respond against increasing ballistic missile threats.

This decision comes after the cancellation of the land-based Aegis Ashore missile defense system, which was scrapped due to various concerns including safety and cost.

The ASEVs will fill the gap left by the canceled Aegis Ashore systems and are expected to play a vital role in Japan’s maritime self-defense strategy. Scheduled for commissioning in 2027 and 2028, these vessels will be equipped with advanced radar and missile defense systems, making them a critical addition to the Japan Maritime Self-Defense Force’s (JMSDF) fleet.

The contracts for building the two ASEVs were awarded to Japan’s leading shipbuilders, Mitsubishi Heavy Industries (MHI) and Japan Marine United Corporation (JMUC). The MHI was awarded the first contract, worth ¥139.7 billion ($980 million), in August 2024, while JMUC received the second contract for ¥132.4 billion ($930 million) in September 2024. The two companies are among Japan’s most prominent defense contractors, both with a strong track record of producing naval vessels for the JMSDF.

Despite the difference in contract values, officials from the Ministry of Defense’s Acquisition, Technology, and Logistics Agency (ATLA) have clarified that the discrepancy is due to variations in parts procurement. The specifications and performance of the two ships will remain identical, ensuring consistent operational capabilities for both vessels.

The first ASEV is expected to be delivered by MHI in 2027, with commissioning scheduled for March 2028. JMUC will follow by delivering the second vessel in 2028, with commissioning slated for March 2029. The construction of these vessels is part of Japan’s broader strategy to modernize its military forces and respond to evolving threats in the region.

ASEVs as a replacement for Aegis Ashore

Japan’s decision to develop the ASEVs came after the government abandoned plans to install Aegis Ashore systems in two locations within the country. The land-based missile defense system faced opposition due to safety concerns, including the risk of rocket boosters falling into residential areas during missile intercept tests. The estimated cost of maintaining and operating the Aegis Ashore systems also raised concerns, leading the government to seek a more flexible, sea-based alternative.

The ASEVs, operating in the open ocean, offer a more mobile and less intrusive solution to missile defense. By replacing the land-based systems with these ships, Japan can enhance its missile defense posture without the risks associated with stationary, land-based installations. The ships will be specifically tasked with ballistic missile defense (BMD) operations, patrolling Japan’s surrounding waters to detect and intercept potential missile threats.

Advanced radar and missile defense systems

One of the standout features of the new ASEVs is their cutting-edge radar and missile defense systems. Each vessel will be equipped with Lockheed Martin’s SPY-7 radar, one of the most advanced radar systems.

The SPY-7 has five times the tracking capability of the SPY-1 radar currently installed on many of Japan’s existing Aegis-equipped vessels. This enhanced capability allows the SPY-7 to track missiles launched on lofted trajectories—a technique used to extend the range of missile strikes—while simultaneously tracking multiple ballistic missiles.

The SPY-7 radar system demonstrated its capabilities during a live test on April 4, 2024, successfully tracking and identifying multiple missile targets. With this technology onboard, the ASEVs will be able to provide comprehensive missile defense coverage, improving Japan’s ability to detect and neutralize potential threats.

In addition to the radar system, each ASEV will feature 128 Vertical Launch System (VLS) cells, capable of launching a range of missiles designed for both offensive and defensive operations. Among these will be the SM-6 interceptor, a versatile missile capable of engaging ballistic missiles, cruise missiles, and aircraft.

The ships will also be equipped with an upgraded version of the Type 12 surface-to-ship guided missile, which is being developed by MHI. The upgraded Type 12 missile will offer extended range and improved precision, providing the ASEVs with formidable counterattack capabilities.

The ASEVs will be developed to intercept and defend against hypersonic glide vehicles, a new class of missile that poses a significant challenge to traditional missile defense systems. Hypersonic glide vehicles travel at extremely high speeds and can maneuver unpredictably, making them difficult to track and intercept. The combination of SPY-7 radar and advanced missile systems will ensure that the ASEVs are prepared to meet this emerging threat.

ASEV are larger and more capable

The ASEVs are not just advanced in terms of technology; they are also larger and more capable than many of Japan’s existing vessels. The ships are designed to be 190 meters (623 feet) long, 25 meters (82 feet) wide, and have a standard displacement of 12,000 tons. This makes them significantly larger than Japan’s Maya-class Aegis destroyers, which are 170 meters (557 feet) long and have a displacement of 8,200 tons.

Initially, the vessel’s size and cost were points of contention within the Ministry of Defense. Some critics argued that the ships were too large and expensive, which could impact their maneuverability and overall operational efficiency. However, the Ministry ultimately decided to proceed with a slightly downsized version of the original design, reducing costs while maintaining the ship’s air defense capabilities.

The larger design allows the ASEVs to carry more advanced equipment and larger quantities of munitions, further enhancing their combat effectiveness. The ships will also be designed to accommodate future upgrades, including the potential integration of new weapon systems as they become available. This future-proofing ensures that the ASEVs will remain relevant and capable for decades to come.

Strategic importance and regional security

The development of the ASEVs comes at a time of heightened tensions in the Asia-Pacific region, with increasing missile tests from North Korea and rising concerns about China’s military expansion. Japan has made it clear that these vessels are being developed primarily as a deterrent against North Korea’s ballistic missile program, which continues to pose a significant threat to the region.

In recent years, North Korea has conducted multiple missile tests, some of which have demonstrated the ability to reach Japanese territory. The ASEVs will serve as a key component of Japan’s strategy to defend against these missile threats, providing a mobile, flexible platform that can intercept missiles before they reach Japanese airspace.

In addition to deterring North Korea, the ASEVs are also seen as part of Japan’s broader effort to enhance its military capabilities in response to China’s growing influence in the region. China’s naval expansion and increasing presence in the East China Sea have raised concerns about territorial disputes and maritime security. The ASEVs will enable Japan to maintain a stronger maritime defense posture, contributing to the overall stability of the region.

As Japan continues to invest in its defense capabilities, the ASEVs represent a significant step forward in ensuring the country’s security in the face of evolving threats. These vessels, equipped with the latest radar and missile defense technologies, will provide Japan with the ability to detect, track, and intercept a wide range of missile threats, from ballistic missiles to hypersonic glide vehicles.

The flexibility and mobility offered by these ships make them a more practical alternative to land-based systems, while their advanced capabilities ensure that Japan can maintain a robust defense posture for years to come. The ASEVs also underscore Japan’s commitment to working closely with its international allies, particularly the United States, which provides much of the technology used in the Aegis system.