An Aegis-class destroyer, Kirishima, recently left Yokosuka port, heading for the Indian Ocean. Two Japanese fast combat support ships (rotating among four), escorted by three destroyers (rotating among six), have been refueling U.S. and other ships engaged in the war on terrorism in Afghanistan. The Kirishima will replace one of the three destroyers currently serving in the region. While proponents of the decision to deploy the Aegis destroyer base their arguments on technical and political grounds, opponents challenge the move on legal grounds, focusing on the constitutionality of collective defense, the Aegis’ extensive air defense capability, and joint operability.