For a long time, the United States and Japan have had strong relationships, they are important commercial partners. The Asian country exports a lot of goods to America, companies like Toyota, Nissan, Honda, and others have a great market in the US. Both countries were enemies during the Second World War, but Japan became a powerful market economy with a democratic system after this. Although the land of the Rising Sun is in Asia, it shares a lot of Western values becoming an important ally of the US. Japan has been a peaceful nation since the end of the Second World War, but there are big challenges today: An aggressive North Korea and a growing China.
Change of policy
Japan was a foe of America, so, when the Asian country was defeated it was forced to have a limited military power. The image of Japan was negative for a long time because it was an aggressor during the Second World War, so, it was forced to have a limited military capability. A change of policy is urgent these days, Japan must develop its military power to face the growing threats from the Pyongyang regime. If Tokyo increases its military power, it will intimidate the North Korean regime and put pressure on its poor economy. Japan has the technology, money, and intelligence to develop advanced weapons and a bigger military force.
Psychological effect
If Japan decides to develop more weapons and join America in the effort to contain Kim Jong-un, this will have a huge psychological effect worldwide.
The United States is seen as a nation that likes to meddle on the issues of other countries, but if an Asian nation joins Washington this will improve the image of America. An Asian country, Japan, would be fighting for the global peace and joining the US in the effort. This will be seen as a global effort, not as an aggressive American policy.
China
We can see that the economic and military power of China keeps growing fast, in a certain moment Beijing could have more territorial ambitions. Besides, China wants Washington to soften its policy with North Korea and in the future, Beijing could try to be more aggressive. If Japan increases its military power this will intimidate Beijing because the Japanese were able to subjugate the Chinese for a long time, Hirohito's army was able to control and dominate China for a long time. The United States has a huge military budget which is putting a lot of pressure on the national economy, Japan could help share the responsibilities and improve the security in Asia.
