The time has come for Japan and the United States to embark on an ambitious co-development project: a long-range ground-based anti-ship cruise missile system. Such a program is strategically necessary, technically feasible, cost effective and politically attractive — the allies should make it a top priority.

Japan and the U.S. face a rapidly growing and modernizing Chinese military. As of January, China’s People’s Liberation Army Navy included 335 vessels and its coast guard fielded another 248 ocean-going ships, to say nothing of Beijing’s huge maritime militia. These numbers are increasing rapidly as China builds some of the world’s largest and most advanced naval combatants.

Moreover, Beijing’s arsenal of cruise and ballistic missiles puts both the allies’ fixed bases and their surface naval forces at additional risk. China has an estimated 1,800 cruise and ballistic missiles with ranges between 500 and 5,500 km (the range previously banned by the Intermediate-Range Nuclear Forces Treaty). The allies have zero.

Projecting power against this array of Chinese capabilities is growing more difficult by the day. The alliance has long been overly dependent on fixed bases and vulnerable surface ships. There is a growing risk that Beijing might believe that it could knock out most Japanese and American forces in a first strike. Reversing these trends and bolstering deterrence will require new thinking.

The U.S. and Japan may find themselves with fewer ships and missiles than China, but they have one tremendous geographic advantage: the Ryukyu Islands. Placing anti-ship cruise missiles on these islands would begin to reverse the deterioration of the regional military balance. After all, the allies are status quo powers, so any Chinese effort to take territory would require the PLA to deploy and sustain its forces across large bodies of water. This is a tall task against a well-prepared opponent.

This strategic logic has led both the U.S. and Japan to develop ground-based anti-ship missile systems. But a co-developed project makes the most sense because it can be technically advantageous, cost effective and politically beneficial.

From a technical standpoint, this system is attractive for co-development because both countries have needed expertise. Japan has developed the Type 12 surface-to-ship missile, as well as concepts of operations for island chain defense. The U.S. has developed advanced long-range missiles, such as the Long Range Anti-Ship Missile (LRASM). Working together, this experience could decrease costs and increase capabilities, including for potential follow-on projects. In particular, Japan could lead on developing a mobile launcher while the U.S. could lead on the missile itself.

As regards cost, co-development has several advantages. Most notably, it increases the total purchase size for a system while largely holding development costs steady. This is the kind of burden-sharing that we should want from our alliances — focused on real capabilities, not cash transfers.

And from a political perspective, co-development can tighten strategic, operational and industrial cooperation within the alliance. Co-development of the SM-3 Block IIA ballistic missile interceptor has been a success, but there is no major follow-on program. An anti-ship cruise missile is a natural fit. Just as SM-3 Block IIA shields Japan against air and missile attack, an anti-ship cruise missile would protect Japan against maritime intrusions.

Some critics will worry that such a program would provide Japan an “offensive” capability, but the reality is that anti-ship cruise missiles are a denial system. They are used to prevent foreign incursions, not to control foreign territory. Projecting power forward would still require other — most likely American — air and naval assets. As a result, an anti-ship missile program should be seen as a continuation of Japan’s long-standing role as the alliance’s shield.

In the face of growing Chinese maritime capabilities, the U.S. and Japan cannot simply sit idle. The alliance must focus on building real capabilities, not arguing over cost sharing. Co-developing a ground-based anti-ship cruise missile system is strategically smart, technically feasible, cost effective and politically sound. A co-development program of this sort would be a “win-win” for the alliance (to borrow a phrase from our Chinese friends). Allied leaders should make this a priority in the months ahead.