The introduction of long-range cruise missiles that the Defense Ministry is seeking in its fiscal 2018 budget runs the risk of being taken as an indication that Japan is looking to acquire a capability to strike enemy bases in the face of the growing threat posed by North Korea's nuclear weapons and ballistic missiles. The government says the cruise missiles are meant for protection of Aegis vessels of the Maritime Self-Defense Force on missile defense missions and for defending Japan's remote islands against enemy invasion, and denies that their introduction reflects any change to the nation's exclusively defense-oriented defense policy. But adding the cruise missiles to the SDF' arsenal should be considered from a more comprehensive viewpoint, including how the move would be perceived by other countries in the region and how that could affect the security situation surrounding Japan.
The Defense Ministry has sought an additional ¥2.2 billion in its budget request for acquiring the JSM missile by Norway's Kongsberg Defense & Aerospace and for research on Lockheed Martin Corp.'s JASSM-ER and LRASM missiles. The JSM, with a range of about 500 km, will be mounted on the Air Self-Defense Force's F-35 stealth fighter and is planned for deployment in fiscal 2021, and the U.S.-built JASSM-ER and LRASM missiles, each with a range of roughly 900 km, will be considered for possible mounting on F-15 fighters.
A cruise missile with a range of 900 km could technically enable Japan to hit North Korea's ballistic missile launch facilities without approaching the Korean Peninsula. Based on a 1956 statement by then Prime Minister Ichiro Hatoyama, the government maintains that when there is a pressing danger of a missile attack on Japan — and when there are no other means to defend the nation against such an attack — a minimum necessary strike on the enemy base to forestall the missile attack will be legally within the range of self defense. Still, the government has so far not obtained the capability for such an attack.