The Japanese Constitution - Chapter 2

Chapter 2 - Renunciation of War

Article 9
Aspiring sincerely to an international peace based on justice and order, the Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as means of settling international disputes.
In order to accomplish the aim of the preceding paragraph, land, sea, and air forces, as well as other war potential, will never be maintained. The right of belligerency of the state will not be recognized.

This is arguably the most famous, the most controversial and the most debated article in the world and deserves a separate post. It prohibits Japan from maintaining its own defense forces and military material.

Since end of the 19th Century, unprovoked Japanese aggression had been quite evident in the East Asia and its crescendo came in Pearl Harbour. Hence the first paragraph makes explicit statements of '...war as a sovereign right...' and '...use of force as means of settling international disputes.' The west always saw Japan as a chaotic, closed country with its own principles differing widely from their own. This article was inserted to change this Japanese ideology and bring in the principles of international peace and justice acceptable to the west.

To achieve this it was important to have leverage over Japan and to keep Japan under the control of west. The best way was to prevent Japan from having any defense forces so that Japan cannot take any aggressive steps against other nations. The right of belligerency is not recognized meaning that the aggressive / hostile route cannot be taken in case of conflicts.

Still, being a sovereign nation, Japan has the right to self-defense and the Japanese people have the right to live in a secure and peaceful environment as mentioned in the preamble. Hence Japan still maintains Self Defense Forces (SDF) and minimal military equipments necessary for this task but is still largely dependent on US for its defense.

Though, I still feel that in the long term this has helped Japan because it did not have to spend on military and hence all its resources were used for the development of the country which made Japan an economic powerhouse in Asia and it is still the world's 3rd largest economy, way ahead of the European countries. Contrast it with many of the developing nations in South and South East Asia which got independence during the same period which faced enormous corruption and expenditure in the defense sector and are still behind Japan in terms of technological capabilities and economic ability.