The NSS is a strategic guideline document for the Japanese government’s policies regarding diplomacy, defense, and economic security for a period of approximately the next 10 years. Based on this, the National Defense Strategy（国家防衛戦略), which outlines the goals of Japan’s defense policy and the means to achieve them, and the Defense Buildup Program (防衛力整備計画), which outlines the scale of the introduction of specific defense equipment and the budget, were newly formulated.
According to the Defense Buildup Program, the Japan Maritime Self-Defense Force (JMSDF) will increase the number of Aegis destroyers (DDG) from the current eight to ten. In addition, two Aegis system-equipped vessels (ASEV), which specialize in ballistic missile defense (BMD), will be deployed separately from these. Thus, by the end of the decade, the JMSDF will have 12 ships equipped with Aegis Weapon System (AWS). JMSDF plans to replace its aging destroyers (DE, DD) with Mogami class FFMs, presumably not only with FFMs but also with DDGs to replace two of these vessels.
Presumably, it was thought necessary to increase the number of Aegis destroyers to protect the fleet from Chinese anti-ship missiles in the event of a future armed conflict with China. The Japanese government has also decided to purchase 500 Tomahawk cruise missiles, which will be installed on JMSDF Aegis destroyers. The FY2023 defense budget request announced on December 23 already includes 211.3 billion yen (about $1.57 billion) for the Tomahawk purchase, which will procure 500 Tomahawks at once. Deployment of the Tomahawk is scheduled to begin in FY2026.
Another 110.4 billion yen (about $820 million) is also requested for the budget to add the necessary modifications to Aegis destroyers to carry Tomahawk. Although it is not specified what specific modifications will be made, it is likely that the Tactical Tomahawk Weapons Control System (TTWCS) from Lockheed Martin will be integrated into the Aegis destroyer. On the website, Lockheed Martin describes the TTWCS as follows;
“Integrated with the ship’s navigation, communication, situational awareness and launch systems, TTWCS provides the capability to execute Tomahawk missile strikes, plan new missions aboard the launch platform, perform engagement planning, launch all Tomahawk missile variants and control in-flight Tactical Tomahawk missiles.”
Also, Aegis destroyers will be equipped with upgraded version of Type 12SSM. The Type 12 SSM originally had a range of about 200 km. The new upgraded version aims to extend the range to at least 900 km, and eventually to 1,200 km. The shape of the missile has also been modified to reduce the radar cross-section (RCS) and make it stealthy. The “Type 12 SSM (Upgraded)” will also implement Up to Date Command (UDTC), which allows the missile to receive information about the target via satellite communications while in flight and more accurately attack moving targets. The Type 12 SSM was originally a ground-launched missile to be equipped by the Japan Ground Self-Defense Force (JGSDF), but the Type 12 SSM (upgraded) will be developed in versions that can be launched from ground, sea, and air, respectively. The version that can be launched from naval vessels is expected to begin deployment in 2027.
Additionally, the FY2023 defense budget request includes funds for the purchase of SM-6 (13.6 billion yen: about $100 million) as a ship-to-air missile to be equipped on Aegis destroyers. In the past, the Ministry of Defense (MOD) has described the SM-6 as a missile primarily to deal with cruise missiles, but the latest budget request positions it as equipment for countering hypersonic glide vehicles (HGVs). This is a response to the fact that North Korea is developing HGVs and China has already deployed them. The U.S. Navy has already conducted simulated interceptions of HGV with SM-6 (FEX-01, March 2020) and is planning to test them with live ammunition.