After been defeated in the second World War, the United State occupied Japan and proposed to the Japanese government a security policy aimed to prevent Japan to menacing its Asian-Pacific neighbors. With the American presence in the country and the creation of the Article 9 of the Japanese Constitution, Japan was forced to legally dismantled its military force.
However, during the Cold War, Japan only participated in ‘collective security’ situations. But was in the first Iraq war, Japan’s government allowed Japanese peacekeeping to participated in the United Nations peacekeeping operation under highly respective conditions.  And after the 9/11 attacks in the United State, Japan sent naval ships to the Indian ocean to support the Americans military in Afghanistan. Nevertheless, in 2015, Japan and the United State signed another revision of the Guidelines for Defense Cooperation. This guidelines discuss a broader role of the alliance between the two countries, that search to promote more security cooperation in the region and around the world. Also, for the first time, that guidelines indicate space and cyber areas for expanding cooperation between the two countries. 
In this way, Japan’s military expansion has gain a new role in a time of elevated threat in the region. The fear of a volatile North Korea and a growing China, has abled Japanese government to changed its security policies. Despite the Japan increased its military power, it remains the most pacifist country in the world’s great powers. Another interest fact is that, Japan spend only 1 percent of its GDP (Gross Domestic Product) on defense, which is the less than a half of the global average of 2.3 percent and Japanese people are more preoccupied with economic issues than its defense spending. 
Japan and Terrorism
Since the 9/11 attacks in the United State, international terrorism has become a huge concern in the world, and Japanese government wasn’t different. Japan’s leaders has increased their talks with Americans authorities in how can its Self Defense Force can be used regarding the terrorism issue. And despite the fact of Japan not be a principal target for global terrorism, the country has not been immune. With the death of the two Japanese journalists, Kenji Goto and Haruna Yukawa, in 2015, by Islamic State militants, became a such tragic reminder for the Japanese nation, 
Japan and the United State have worked together as allies in the region to reduce threats of terrorism, however, despite of the efforts, there are some groups who have been affiliate with the Islamic State, groups like, Abu Sayyarfand, Mujahidin Indonesia Timor (MIT) have rallied around ISIS cause and promoting Filipinos, Indonesians, and Malaysian to travel to Iraq and Syria. In addition to those foreign fighters from the region who have been joined the Islamic State, some documented have revealed that some Japanese people have demonstrated interested in join the jihad Islamic State, which has provided to the Japanese government some cautions and more vigilant in certain individuals. 
But also, Japan’s role as an economic power could be susceptible as possible terrorist target. In this way, militants recognize the strategic value of economic centers, therefor its destruction could bring a global repercussion. However, despite of the Japanese government be conscious about its alliance or coalition with the United Sate and the effects to its national security, most of the Japanese citizens approve the country’s defense partnership with the United State. 
In the region, Japan plays a leadership role within the Association of Southeast Asian Nations (ASEAN) on several issues, included regional security. In 2006, it was created the ASEAN – Japan Counter-Terrorism Dialogue (AJCTD), which addresses a several range of issues like, money laundering, aviation security, inland water management, conflict resolution and anti-terrorism. Also, the document includes a number of ways of how they should cooperate, like sharing informations to combat terrorism, illicit drug trafficking, cybercrime and collaboration on international economic crime.