Most Japanese do not realize that the Japan-U.S. Security Treaty is a military alliance pact. Unlike a conventional military alliance treaty, however, the pact is not based on reciprocal obligations. For the U.S., the treaty is unfair and is not really bilateral.
In a military alliance, partners share the same destiny; people of a participating nation must be ready to die for those of its allies.
Under the security pact, if Japanese ships are attacked in Japanese waters, the U.S. forces are obligated to repel enemy forces; if U.S. ships are struck in Japanese waters, Japanese Self-Defense Forces will be required to protect them from the enemy. But reciprocity ends there. The treaty stipulates that if Japanese ships are attacked outside Japanese waters, the U.S. forces must help Japan. But if U.S. ships are struck outside Japanese waters, Japan will have no reciprocal obligation.