From @PacificCommand

Secretary Tillerson met with two key strategic allies - #Australia and #Japan - for trilateral strategic talks.

Japan has been largely pacifist since WWII. During Gulf War I, Japan's contribution mainly consisted of financial support, and for Gulf War II, Japan send some unarmed soldiers that Australian soldiers had to protect.

It also hosts US military bases, and pays some of the cost involved, but I assume the stated purpose of those bases are to protect Japan. And Japan and the US espouse similar values (capitalism, rule of law, and democracy), but I'm not aware of those things making two countries allies.

Why does the US government call Japan an ally, let alone a "key strategic ally"?

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    Because "ally" has more definitions than "somebody who'll fight at my side". Commented Aug 13, 2017 at 22:02
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    Also Japan mustn't act aggressively. That was part of what was imposed on Japan's constitution after WWII. They are prohibited from having any standing offensive forces. While they do have some though nowadays (well most forces can be used defensively and offensively, duh), they are part of the self defense army and are only to be used defensively... Thus Japan can only act with military forces once they are attacked - or they violate their own constitution.
    – Adwaenyth
    Commented Aug 14, 2017 at 5:37
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    The US and Japan are formally allied through the Treaty of Mutual Cooperation and Security between the United States and Japan. en.wikipedia.org/wiki/…
    – Ross Ridge
    Commented Aug 14, 2017 at 6:03
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    Those Japanese bases were quite important during the Korean War, and, I assume, during the Vietnam War. Commented Aug 14, 2017 at 14:52
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    @ThomasAndrews and the Cold War. The Sovs would have loved to have taken over the whole of the Far East.
    – RonJohn
    Commented Aug 15, 2017 at 23:49

5 Answers 5


Japan and Australia are both MNNAs (major non-NATO ally)

Japan allows the US to have large bases on its territory, that alone makes it a major ally. The ability to station troops, aircraft and harbour battleships in Japan is of strategic importance in the American policy of military superiority in the Pacific. To allow a foreign power to station its military in your own country is about the closest two countries can be allied. This is much more significant the merely fighting on the same side in a war.

Japan and the US engage in intelligence sharing, joint training, share technological know-how.

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    Reminder to commenters to focus on the question. The general question of Japan/US relations can be discussed in chat.
    – James K
    Commented Aug 14, 2017 at 6:43

Short version...

After WWII, three important things happened:

  1. Japan's military forces were disbanded
  2. A revised Japanese Constitution was drafted which included Article 9, forbidding the establishment of a military body for the purpose of waging war on another country.
  3. As part of the post-war rebuilding, Japan became an occupied territory under the control of the USA.

The third item is particularly interesting, not only did US forces occupy Japan, they carried out a systematic rebuilding and revitalising process, helping the country recover from the war and end up coming out at the end in a strong condition. Since item 1 meant Japan (like the other Axis powers) had no capacity to defend itself, the victorious states agreed to protect them from aggression. Thus the US-Japan relationship became very strong over time, it's probably one of the better examples of two bitter enemies setting aside their past and working together for a better future.

It's not exactly fair to suggest Japan is defenceless though, as pacifism suggests. Article 9 is generally interpreted that Japan is forbidden from initiating a conflict, but it is allowed to engage in self-defence. To that end Japan does have a military body, the mentioned JSDF, which is actually quite capable and has strong backing from the US throughout its development.

Your mention of Gulf War II is a little off base. They weren't unarmed, but rather given instructions to only open fire if fired upon. Additionally, their protection was partially provided by the US trained Japanese Special Forces. There presence was for reconstruction purposes, so they didn't really have much need to engage in offensive action.

Of the countries in the Pacific and East Asian theatre, Japan and South Korea are the two with the strongest ties to the US government. Since South Korea is a terrible place to build a peace keeping force, Japan is the obvious choice for a primary ally in the area. Particularly since the mutual defence treaties are still in place, giving NATO permission to violently oppose any military actions by NK, Russia or China that are considered to be a declaration of war against Japan.

  • Hm, I think the mutual defense treaty is purely between the US and Japan. Japan and Australia have been working on their own mutual defense treaty but as far as I know there is not one involving Japan and NATO (or even, individually, other NATO members).
    – JamieB
    Commented Aug 3, 2022 at 14:26

Some data on United States and Japan cooperation.

  • The United States is Japan's largest largest economic partner while Japan is the US's 4th largest trading partner, with trade totalling an estimated $270.7 billion in 2016.
  • The number of US troops based in Japan is more than in any other foreign country, an estimated 54,000 troops is stationed in the country, part of the United States Pacific Command.
    • One of the reason is that it's stated that Japan is not allowed to form a conventional military, after their defeat in WWII. Rather, the US promises to defend Japan, thus the large number of troops. However, it's still worth noting that Japan has an equivalent of a military, called the Japan Self-Defense Forces, which is essentially their de facto military force.
    • Japan is also the cornerstone of the US's security interests in Asia.
    • The United States, too, was well-served by the alliance. America needed a strong Japan as a regional partner, where it served as an anchor on the far side of the Pacific and a gateway to Asia. Washington was able to station large air and naval forces off the coast of Asia where they were invulnerable to ground attack, and use them to fight communism on the mainland.

      (emphasis mine)

      — The Alantic

Some other areas of cooperation (from the Fact Sheet by the US State Dept.):

  • development assistance
  • global health
  • environmental and resource protection
  • women’s empowerment
  • science and technology
    • brain science
    • aging
    • infectious disease
    • personalized medicine
    • international space exploration
  • people-to-people
    • education
    • science

Thus, both countries cooperate on a wide range of issues, thus Japan's considered a key strategic ally to the US.


The general co-operation between the United States and Japan is covered well in the other answers.

However regarding a "largely pacifist" Japan, this view seems to stem primarily from Article 9 of the Japanese Constitution in which:

the state formally renounces the sovereign right of belligerency and aims at an international peace based on justice and order.

However, it's worth noting that Article 9 was amended (somewhat controversially) in July 2014 by Article 96 in which:

the Japanese government approved a reinterpretation which gave more powers to the Japan Self-Defense Forces, allowing them to defend other allies in case of war being declared upon them, despite concerns and disapproval from mainland China and South Korea, whereas the United States supported the move

This would seemingly allow Japan to join war defensive wars the US is involved in, perhaps adjusting the prevailing "largely pacifist" view of Japan.


I guess the fact that they stand on the same side when it comes to global (and some regional) political en military matters makes them allies.

In the current time frame I guess the most obvious matter would be that they both are opposed to North-Korea's nuclear programme.

Apart from that, I would guess the bases in Japan are not only for the protection of Japan, but they serve a strategic purpose for the defence of the US as well, in the same way Her Majesty's Navy built a base on the island of Saint Helena - that surely wasn't done to protect the island (a barren, uninhabited piece of vulcanic rock at the time, in the middle of the Atlantic Ocean).

Apart from that, after the "you're either with us, or against us"-rhetoric, I guess you are either an ally or an enemy of the US. And I don't think the US wants to make an enemy out of one of the more powerful industrialised nations on earth, especially when they are providing them with a strategic foothold on the Asian continent.

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    "I guess you are either an ally or an enemy of the US." That's simply not true. There are 121 members of the Non-Aligned Movement.
    – ceejayoz
    Commented Aug 13, 2017 at 22:44
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    @ceejayoz I am sure there is some middle ground between being an ally or an enemy, but I am not convinced that membership of the NAM is relevant to that middle ground. In the last decade, the NAM was presided over by the leaders of Cuba, Egypt, Iran and currently Venezuela. At least three of those countries are not on the current US ally list. Two face threats of (increased) sanctions and one even was threatened very recently with military invasion by the US. I never said I agreed with the "you're with us or against us"-rhetoric, but such words have consequences.
    – oerkelens
    Commented Aug 14, 2017 at 5:43

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