Photo/IllutrationMembers of the 31st Marine Expeditionary Unit conduct an assault drill in the Philippine Sea. (Provided by the U.S. Marine Corps)

  • Photo/Illustraion
  • Photo/Illustraion
  • Photo/Illustraion
  • Photo/Illustraion

A key unit of the U.S. Marine Corps stationed in Okinawa Prefecture is repeatedly conducting drills overseas, U.S. archives show.

The 31st Marine Expeditionary Unit (31st MEU), which is deploying widely from East Asia to the Middle East, has also placed importance on disaster rescue operations in recent years, the records show.

The 31st MEU has visited or deployed to at least 15 countries while using Okinawa Prefecture as its base of operations.

The Okinawa prefectural government has made the 31st MEU's frequent absences from the prefecture one of the reasons for its assertion that there is no geographical necessity for Marine Corps bases to be located in Okinawa.

The Marines disclosed its Command Chronology that records unit deployments at the request of The Asahi Shimbun.

Annual reports and related documents from 1992, when the 31st MEU was reactivated, to 2017 were obtained. The total number of disclosed pages was about 3,600. (Parts of the reports and related documents from 2004 to 2005, in 2008, and from 2012 to 2015 did not exist or were not disclosed.)

According to the disclosed documents, the 31st MEU left Okinawa for other regions of the world more than 100 days a year in most of the years. The largest number of days was about 160 in 2009.

Since there were some cases in which the unit’s whereabouts were unclear, the number of days in which it was outside Okinawa could be longer.

In most of its absences from Okinawa, the purposes were for drills in other areas or countries, such as the U.S. territory of Guam, South Korea, Thailand and Australia.

In and after 2001, the unit often deployed to Southeast Asian countries for disaster rescue operations.

Meanwhile, the 31st MEU left Okinawa to respond to emergencies twice, in 1998 and in 2004.

In 1998, the unit was dispatched to Kuwait following the U.S. and British forces’ aerial bombing of Iraq. In 2004, it was deployed to Fallujah in Iraq where fierce fighting occurred.

Under the Japan-U.S. Security Treaty, the United States has a duty to defend Japan while Japan provides land for U.S. bases.

As for the Marine Corps stationed in Okinawa, Prime Minister Shinzo Abe said, “The corps are a deterrent force of the Japan-U.S. alliance and its core.”

Regarding the 31st MEU, the Japanese Defense Ministry said, “It possesses high capabilities for quick responses.”

Masaaki Gabe, professor of political science at the University of the Ryukyus, who has detailed knowledge of the Japan-U.S. Security Treaty and the U.S. military base issues, said that the archives support the belief that the 31st MEU often leaves Okinawa for long periods by boarding amphibious assault ships and conducts drills outside Japan.

In the event of emergencies around Japan, however, it would be virtually impossible for the 31st MEU to deal with them alone. The U.S. Navy and Air Force would need to be deployed from areas such as Hawaii and Guam, he said.

“The Japanese government says that the U.S. Marine Corps stationed in Okinawa is a deterrent force and that the corps are stationed for the benefit of Japan. But this is only rhetoric to put Japanese people at ease,” Gabe said.

According to the professor, though the 31st MEU is leaving Okinawa for such long periods, the public is not discussing that its deterrent effect has lessened. There would be no problems even if the 31st MEU’s base of operations is in Darwin, northern Australia, or Guam, he said.

“Why doesn’t discussion on the U.S. Marine Corps in Okinawa deepen? For many Japanese, there is only the abstract view that the U.S. forces are necessary. It is difficult for them to see which units are moving to where,” Gabe said.

The Marine Corps stationed in Japan numbered about 20,000 members as of December 2018. Of these, about 2,000 belonged to the 31st MEU. Its main duties are quick responses to emergency situations.

The unit’s members, mainly troops, are replaced by those from the U.S. mainland in a six-month rotation. They board three or four vessels, including amphibious assault ships of the U.S. Marines' Sasebo Base in Nagasaki Prefecture, and work in groups for quick amphibious responses.

The 31st MEU is headquartered in Camp Hansen located in and around Kin, Okinawa Prefecture, and is operating Osprey tilt-rotor transport aircraft in the U.S. Marine Corps Air Station Futenma in Ginowan, also in the prefecture.

The agreement reached between Japan and the United States in 2012 about the realignment of U.S. forces decided that the 31st MEU would remain in Okinawa even after the realignment as a major and the only ground fighting unit.

If new military facilities are constructed in the Henoko district of Nago, also in Okinawa Prefecture, and take over the functions of the Futenma air station, the air squadron of the 31st MEU will use them.

In a news conference in 2012, Satoshi Morimoto, then defense minister, said that while militarily it is not necessary for the U.S. Marines to be stationed in Okinawa, politically, the prefecture is the best location.

“Since then, seven years have passed. Now there are many cases in which China has made maritime advances. Therefore, the significance of the deterrent power of the U.S. Marines stationed in Okinawa has increased,” Morimoto said.

According to Morimoto, Japan is the only country where the Marines are deployed permanently outside the United States. That is because a military dispute is most likely to occur in the area from the Middle East to the Indo-Pacific region.

The role of the Marines stationed in Japan is to prevent military disputes in this wide area, respond to military disputes that occurred and defend Japan along with the Japanese Self-Defense Forces, he said.

“(The 31st MEU is leaving Japan for long periods.) But if it was always staying in Okinawa where its command center is located, the unit is meaningless,” Morimoto said.

“It is a matter of course that the unit leaves Okinawa for long periods when tense political situations continue,” he added.