This expected purchase of an Aegis Ashore system seems to make sense considering it can provide a persistent missile defense capability for Japan without having to rotate in and out their current Aegis BMD ships:
Japan is planning to deploy a new U.S.-developed ground-based missile defense system.
The Defense Ministry is to provisionally request that the fiscal 2018 budget cover planning costs for installing the Aegis Ashore system, according to a ministry official. “We are being urged to enhance our capabilities to continually protect the entirety of Japan from the threat of a missile attack,” the official said. (……)
Japan’s Defense Ministry has studied whether to deploy the Terminal High Altitude Area Defense, or THAAD, system or the Aegis Ashore shield. But it has not planned for Aegis Ashore installations. The system is not included in the current National Defense Program Guidelines or mentioned in mid-term defense planning documents. The official said Aegis Ashore plans will be finalized by the end of the year. [Asian Review]
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