The 60th anniversary of the revised Japan-U.S. security treaty fell on Jan. 19. When it was revised in 1960, popular protests against the treaty gathered momentum. Massive demonstrations surrounded the Diet day after day, and a female student was crushed to death in the disturbance. Even though the revised treaty was eventually approved by the Diet, Prime Minister Nobusuke Kishi was forced to resign and a scheduled visit by U.S. President Dwight Eisenhower was canceled.

What happened 60 years ago may appear to belong to another age, but it's still worthwhile to get a general overview of Japan's national security challenges from a historical perspective.

Since ancient times, governments have made enormous efforts to ensure the safety of their societies, mainly through the buildup of military power and the development of alliances.