While a preemptive-strike capability for Japan isn’t impossible, it is more difficult than many observers realize. Building the force necessary for prosecuting an air campaign would certainly necessitate busting the 1 percent GDP cap on defense spending that Japan currently has in place, but like the prohibition on “offensive” weapons, that too is a policy matter that can be reversed. Another, less lethal national security concern is Japan’s debt problem, which is currently north of 200 percent GDP. Whatever path Japan decides to take won’t be easy.

It’s Japan’s ultimate nightmare: a RQ-4 Global Hawk belonging to Japan’s Air Self-Defense Force (JASDF) is watching a North Korean medium-range ballistic missile being readied for launch. The missile is being fueled, a process that can take hours. The incident follows days of incendiary North Korean rhetoric about Japan disappearing in a “wall of nuclear flames.” Reluctantly, Japan’s prime minister approves a preemptive strike designed to destroy the missile before it is ready for launch.

(This first appeared in May.)

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The scenario above is fiction, particularly Japan’s ability to launch a preemptive strike. But what if Japan could launch such an attack, and what would the East Asian country require to ensure the strike was a success?

As one of the few pacifist countries in the world, Japan maintains the absolute minimum military capability to defend itself. This includes, among other things, a lack of weapons traditionally viewed as offensive in nature such as intercontinental ballistic missiles, long-range bombers and aircraft carriers. As the only country to be the target of a successful nuclear-weapons strike, it has a strong anti-nuclear-weapons policy.

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These policies have served Japan fairly well for the last seventy years, but recent developments in North Korean nuclear weapons and missile programs have complicated matters. Japan has set up a tiered ballistic-missile defense system, with SM-3 Block 1B interceptors on board Aegis destroyers providing area protection of the Japanese islands, and Patriot PAC-3 protecting specific targets, notably including Tokyo. While this system would likely prove effective, Japan has so far limited itself from a more proactive solution: preemptively destroying enemy missiles before they can be launched.

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That may be changing. In recent years, responding both to North Korea missile threats and a dispute with China over the Senkaku Islands in the East China Sea, Japan has been loosening its policy on offensive weapons. A new unit of Japanese marines, previously forbidden as an offensively oriented military organization, was rebranded as a defensive organization—so long as it was used to take back Japanese territory forcibly taken by another power.

Over the past several months, reports have twice emerged that Japan has planned to purchase antisurface missiles in order to strike a North Korean missile before it can be launched. In May 2017, the newspaper Sankei Shimbun claimed the government of Prime Minister Shinzo Abe wanted to purchase Tomahawk land-attack cruise missiles. In June, the Tokyo-based Yomiuri Shimbun reported that the Norwegian-developed Joint Strike Missile, which can fit internally in the weapons bay of the F-35 fighter, was a “promising candidate” for Japan’s planned F-35A Joint Strike Fighter fleet.

The Japanese government denied both reports, but it is well known that the current government would like a more proactive means of dealing with the threat of North Korean nuclear weapons. Like the new Japanese amphibious unit, it would be an offensive weapon to be used “defensively.” What would such a preemptive-strike capability look like?

A preemptive strike sounds like a bold and decisive plan, but the truth is more complicated. A Japanese strike would be the beginning of a North Korean–Japanese war, especially if North Korean leader Kim Jong-un survives the initial attack. Japan will have stirred up a hornets’ nest on the first day, and will likely need to conduct a full-scale air campaign several weeks long, just to ensure that it destroys as many mobile missiles as possible. A single missed missile launcher could spell disaster for Japan down the road. There will be a first surprise strike, but also a third, fourth, fifth and probably twentieth strikes.

The first step to building capability is to increase Japan’s intelligence, surveillance and reconnaissance assets, not only to detect imminent launches but also to monitor North Korea’s fleet of mobile missile transporters and launchers. In particular, it would need even greater satellite surveillance capabilities than it has now and more high-altitude, long-endurance drones than the three RQ-4 Global Hawks it plans to purchase. While these are restrained by North Korea’s limited road network—the country only has five hundred miles of paved roads—keeping track of them is vital, especially after a preemptive strike. If North Korea hadn’t meant to launch a ballistic missile, after a Japanese attack it will almost certainly do so.

The second step is to acquire precisely the weapons the Japanese government has denied wanting in the past: Tomahawk and Joint Strike Missiles. Tomahawks could be launched against known North Korean nuclear facilities, while F-35As armed with Joint Strike Missiles could be sent to chase down mobile launchers that escape the cruise-missile attack.

Meanwhile, Japan would place a considerable amount of airpower into the skies in the form of a full-on air campaign. A combat air patrol of F-15Js could protect the F-35s and other Japanese warplanes from the North Korean People’s Army Air Force and even possibly Chinese interference. Japanese combat search-and-rescue forces would loiter off the North Korean coastline, ready to scoop up downed pilots. All of this would require a lot of aviation fuel, and Japan’s tiny fleet of four KC-767J aerial refueling tankers is nowhere near enough to handle the task. A force of up to twenty tankers working in shifts would be necessary to both support a Japanese aerial armada and keep an eye on other hot spots, particularly the East China Sea.

An air campaign over North Korea would be an enormously complex undertaking, but the alternative could be hundreds of thousands of dead Japanese civilians. North Korea is estimated to have ten to twenty weapons. Even just three nukes would kill more than 150,000 Japanese citizens, as well as Koreans, Chinese, Americans, Canadians and other visitors from around the world. A North Korean nuclear strike against government buildings in Shinjuku, Tokyo would kill sixty thousand people and injure 106,000 more. A strike on Osaka would kill fifty-three thousand and injure 117,000 more. A nuclear attack on the JASDF headquarters at the American Yokota Air Base would kill twenty thousand and injure forty-five thousand.

While a preemptive-strike capability for Japan isn’t impossible, it is more difficult than many observers realize. Building the force necessary for prosecuting an air campaign would certainly necessitate busting the 1 percent GDP cap on defense spending that Japan currently has in place, but like the prohibition on “offensive” weapons, that too is a policy matter that can be reversed. Another, less lethal national security concern is Japan’s debt problem, which is currently north of 200 percent GDP. Whatever path Japan decides to take won’t be easy.

Kyle Mizokami is a defense and national-security writer based in San Francisco who has appeared in the Diplomat, Foreign Policy, War is Boring and the Daily Beast. In 2009 he cofounded the defense and security blog Japan Security Watch. You can follow him on Twitter: @KyleMizokami.

Image: Reurters.