By Kei Ishinabe

U.S. President Donald Trump’s remark that the Japan-U.S. Security Treaty is “unfair” caused a stir in Tokyo and Washington. Setting aside what the true intent of the statement may have been, it is easy for the treaty to set off criticism that Japan is a “security free rider” because of the treaty’s structure which requires only the U.S. military to defend Japan [and does not place an equivalent obligation on Japan]. The treaty stipulates, however, that Japan provides the U.S. military with bases for the stability of the Far East region. It is for this reason that the Japanese government takes the position that, as Chief Cabinet Secretary Yoshihide Suga put it recently, “the obligations of Japan and the U.S. are well-balanced and the treaty is not one-sided.”

Japan’s share of the costs of hosting U.S. military bases is much larger than that of any other U.S. ally. According to a report released by the U.S. Department of Defense in 2004, Japan incurred as much as about 75% of total costs in 2002. Though the U.S. has not issued such a report since then, a survey conducted by National Defense Academy professor Yasuhiro Takeda shows that the percentage dropped to 63% in 2015 but rose to 70% in 2017. Japan has earmarked some 590 billion yen in this year’s budget as costs related to hosting the U.S. military and is spending the money to rent the land [for the bases] and for measures to reduce the burden on base-hosting municipalities.

Also, Japan accepts “limitations on national sovereignty” by providing the U.S. military with bases. This obligation is notable in Okinawa Prefecture; 70% of the Japanese land area used for U.S. military exclusive-use facilities is in Okinawa. Prime Minister Shinzo Abe says: “Having bases in Japan enables the U.S. to protect peace and stability in the world while protecting its own interests. I have explained to President Trump that the treaty is reciprocal and he has been convinced,” underscoring that it is a common understanding between the two leaders.

But if Japan has to review its share of the costs of stationing the U.S. forces in response to President Trump’s request that it shoulder “a fair share of the burden,” how will the Self-Defense Forces and the U.S. military divide the roles and responsibilities?

Takeda says: “A realistic scenario is for the SDF to play a part in the U.S. military’s responsibilities and the Japanese government to simultaneously reduce the limitations on national sovereignty while keeping the Japan-U.S. Security Treaty as a cornerstone.”

In his book Costs of the Japan-U.S. Alliance (published by Akishobo), Takeda lists “defense against ballistic missiles,” “defense of sea lanes,” and “ defense of islands” as duties the SDF could perform in place of the U.S. military and estimates that this would require some 1.6589 trillion yen a year.

In defending against ballistic missiles, Japan needs to introduce early-warning satellites and electronic warfare aircraft to equip itself with the capabilities to detect and track missiles and attack enemy bases, for which Japan currently depends on the U.S. Takeda estimates that approx. 567.5 billion yen is required to acquire a “Terminal High Altitude Area Defense (THAAD) missile” for improving Japan’s ability to intercept missiles and protect citizens by minimizing damage.

As for defending sea lanes, Takeda points out the need for Japan to take over as much as possible the duties of the U.S. Navy’s 7th Fleet, which covers the Indo-Pacific region. He estimates some 883 billion yen is needed for that.

In defending outlying islands, Japan will need to strengthen the readiness of the Amphibious Rapid Deployment Brigade, which is tasked with recapturing islands from invaders, by spending roughly 208.4 billion yen to introduce a landing ship or a transport ship. At the same time, Japan will reduce the limitations on its national sovereignty by having the SDF take over the control of facilities on U.S. military bases in Okinawa and having Japan and the U.S. jointly use the facilities.

The total amount of 1.6589 trillion yen is equivalent to 0.3% of the gross domestic product (GDP). The current defense spending accounts for about 1% of GDP, making the sum roughly 1.3%. Takeda says, “What is important is an attitude to seek an appropriate balance between the alliance and self-defense.” (Slightly abridged)