The U.K. Ministry of Defence has revealed that British troops are training on U.S. military bases in Okinawa. The disclosure, made in response to a request under the U.K. Freedom of Information Act, is the first documentary proof that the U.S. military is using its bases in Japan to train third-country forces, a move that may breach the Japan-U.S. Security Treaty.

According to the Royal Navy Command Headquarters in Portsmouth, England, since January 2015 two Royal Marine lieutenants have been embedded with the U.S. Marines and deployed to U.S. Marine Corps Camp Schwab, in the northern city of Nago, and USMC Camp Hansen, in the central Okinawan town of Kin. While in Okinawa, they have "conducted jungle and range training" in a program approved by the Commandant of the U.S. Marine Corps and the Commandant General Royal Marines.

The 56-year-old Japan-U.S. Security Treaty, under which Pentagon troops are stationed in Japan, does not provide for the training of foreign forces at U.S. bases here. The only exceptions are seven U.S. bases categorized as United Nations Forces installations, but neither Camp Schwab nor Camp Hansen is designated as such.