The U.S. and Japan began the biennial Keen Sword exercise at military installations throughout Japan and surrounding waters.
Japan and the United States have successfully tested the Aegis ballistic missile defense system on Tuesday.
Japan’s picked a new $1.2 billion radar for its two ground-based Aegis ballistic missile defense sites.
The price for two Aegis Ashore batteries could exceed $5.4 billion -- over twice the amount initially cited by the Japanese government.
The announcement contrasts with long-term moves to increase Japan's missile defense capabilities.
Move part of Japanese fortification of first island chain against Chinese fleets.