Japan’s plans to acquire cruise missiles for its combat aircraft are a step forward in its ability to provide for its own defence. But these weapons won’t give the country the capacity to pre-emptively destroy North Korea’s ballistic missiles because of the major weaknesses in Japan’s ability to locate mobile targets.

Tokyo’s announcement ^[1] that it will fit its soon-to-enter-service F-35A fighter force with the 500-kilometre-range Joint Strike Missile capped a year of significant developments for Japan’s military. It’s also studying options to fit its existing F-15J fleet with 900-kilometre-range air-to-surface missiles and 560-kilometre-range anti-ship missiles. With a record budget ^[2] proposed, the procurement ^[3] of a new land-based anti-missile system confirmed, and the election of a parliament predisposed to moving Japan away ^[4] from its pacifist constitution, the scene seems set for a new era in the country’s approach to security. Given North Korea’s repeated firing of ballistic missiles over Japan, it also appears clear where much of Tokyo’s new offensive capability is to be aimed.

Japan denies ^[5] that the cruise missiles are for use against North Korean facilities. The country’s defence minister, Itsunori Onodera, said at the procurement decision announcement, ‘The stand-off missiles we are introducing at this time are purely for our national defence and are not for the purpose of attacking enemy bases.’ Instead, Tokyo claims the weapons are to be used if enemy forces try to attack or succeed in occupying Japan’s outlying islands, and to protect units of the Japanese Maritime Self-Defence Force. Nevertheless, Onodera has long been a proponent ^[6] of giving Japan the ability to strike North Korean targets.  The explanation offered for current plans is likely simply a political ploy to smooth over objections.

More concerning are the practicalities of the Japanese Air Self-Defence Force (JASDF) striking North Korea’s missiles while they’re still on the ground. As demonstrated during the 1991 Gulf War’s ‘Scud hunt ^[7]’, finding and destroying mobile missile platforms—known as transporter-erector-launchers ^[8] (TELs)—and their support vehicles is a difficult and time-consuming process. Although sensor technology has vastly improved in the last quarter century, a comprehensive search operation would be largely dependent on deploying a fleet of unmanned aerial vehicles (UAVs) and using satellite surveillance ^[9] to provide targeting data in real time. Japan currently lacks long-range UAVs and has only a limited satellite network ^[10], meaning that it would be reliant on third-party information to conduct air strikes on mobile targets. Although in theory Tokyo could send crewed combat aircraft (particularly the F-35A once it enters service) into North Korean airspace on search-and-destroy missions, that would be hazardous in the initial stage of a conflict, likely provide only limited results and waste the stand-off capability of its cruise missiles.

There’s no easy remedy to this surveillance shortfall, and even the US would face difficulties in gathering the data required. The majority of the platforms available to Washington are UAVs such as the RQ-4 Global Hawk ^[11] (three of which Japan is purchasing) and the MQ-9 Reaper ^[12]. These aircraft—lacking speed, manoeuvrability and stealth—could be shot out of the sky ^[13] in the type of non-permissive environment that even North Korea’s elderly (but likely still capable ^[14]) air defence system ^[15] would present during the opening phase of the war. Crewed surveillance aircraft such as the U-2 and E-8 Joint Surveillance Target Attack Radar System would also be threatened in the early days of a conflict. The US is hurriedly trying to remedy the situation by fielding the seldom-seen stealth RQ-170 Sentinel ^[16] and larger RQ-180 ^[17] UAVs. But deploying them into theatre would take time and there aren’t many of them.

Even if the surveillance assets were available, there are still major challenges to overcome. North Korea’s missile force has had decades to prepare bunkers—some of which may not be breachable by relatively small cruise missile warheads—and other protective measures. It seems probable that personnel will be well drilled in doing what it takes to leave cover, prepare and fire a missile, and then escape in as little time as possible. With several dozen TELs—some of which are now tracked ^[18] to allow them to drive off-road—for hundreds of Hwasong-7/Nodong-1 missiles, inflicting meaningful attrition quickly would be challenging. This situation will only be made worse when the Pukguksong-2 ^[19]—which is solid-fuelled and so can be launched with only a few minutes’ preparation—enters service.

Japan’s limited ability to hit missiles threatening the country doesn’t mean that there wouldn’t be worthwhile targets for Tokyo’s cruise missile force to engage in the event of a conflict. Options would include hitting known above-ground missile assembly, testing and storage facilities. Strikes on such fixed locations by the JASDF would also free up more capable US aircraft to attack mobile and time-sensitive targets like TELs. But Japan’s acquisition of cruise missiles doesn’t in itself convey the ability to destroy North Korea’s most powerful weapons.