After all, under the Japan-U.S. Defense Cooperation agreement, Japan's Self-Defense Forces would be allowed to engage for the first time in detailed planning with U.S. forces to meet a range of contingencies, including non-combat support, in the event of conflict in the East Asian region.

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Such a step would allow Japan's Self-Defense Forces to launch a pre-emptive missile strike at an enemy's military target when an imminent attack on Japan from that specific site is confirmed, officials for the ruling Liberal Democratic Party said.

WSJ: Japan's Military Moves Toward Pre-Emptive Strike Capability

Article nine of the constitution forbids Japan's military -- the Self-Defense Forces -- from waging war overseas.

CNN: Japan ground troops set to leave