Japan’s Integrated Air and Missile Defense and Counterstrike Policy

A ballistic missile is a weapon launched by a rocket engine that then travels along a parabolic ballistic trajectory. Japan’s ballistic missile defense is fundamentally a layered defense system that coordinates upper-tier interception by Aegis ships and lower-tier interception by Patriot PAC-3 through the JADGE automated warning and control system.

Japan began developing its missile defense system in fiscal year 2004 (Heisei 16) to respond to missile attacks and other threats. It is developing an independent framework for responding to ballistic missile attacks by equipping Aegis ships with ballistic missile response capabilities and deploying PAC-3 units.

In recent years, surrounding countries have significantly expanded their missile capabilities in both quality and quantity, and repeated missile launches have made missile attacks against Japan a real threat.

As threats diversify, it is becoming more difficult to respond fully using only conventional missile defense networks. Japan is therefore working to establish a framework that fundamentally strengthens detection, tracking, and interception capabilities while enabling various sensors and shooters to be operated centrally and optimally.

Under integrated air and missile defense, strengthened missile defense networks provide interception while counterstrike capabilities constrain the adversary’s missile launches, thereby seeking to deter missile attacks themselves in conjunction with missile defense.

Strengthening stand-off defense capabilities also relates to the ability to address vessels and landing forces invading Japan, including its islands, from outside the threat zone.

For responding to ballistic missiles, Japan maintains a layered air defense system consisting of 8 Aegis ships and PAC-3 units nationwide. PAC-3 units are deployed in dispersed locations throughout Japan to protect Aegis ships and key facilities, and are maneuvered and deployed according to circumstances.

When destruction measures against ballistic missiles or other threats are ordered, Japan responds effectively under the unified command of the Commander of the Joint Operations Command through JADGE and other systems.

Surrounding countries and others are increasing the concealment and immediacy of launches by using diverse platforms, including transporter-erector-launchers (TELs) and submarines. Their precision-strike capabilities are also improving.

New threats include ballistic missiles that fly at low altitudes along irregular trajectories; hypersonic glide vehicles (HGVs), which are launched from ballistic missiles and are said to glide and maneuver at hypersonic speeds after reentering the atmosphere; and hypersonic cruise missiles (HCMs), which enable hypersonic flight through technologies such as scramjet engines.

Integrated air and missile defense seeks to establish a framework that connects various sensors and shooters through networks and operates them centrally and optimally. Based on the National Defense Strategy and other policies, counterstrike capability is defined as the ability to deliver effective counterstrikes in the adversary’s territory as the minimum necessary self-defense measure to prevent attacks, making use of stand-off defense capabilities and other means.