TOKYO (Kyodo) -- The U.S. Air Force conducted at least 150 loading drills for nuclear weapons in Okinawa in the first half of 1957 not far from civilian areas, declassified documents show.
The 1955-1964 annual reports by the 313th Air Division reveal that Okinawa, which was under U.S. control at the time, was used as a strategically important base for the military to prepare for the use of nuclear weapons in Asia in the midst of the Cold War.
According to the 1957 report of the division, which was operating the Kadena Air Base, personnel of the 12th Aviation Depot Squadron were trained to offload nuclear weapons from arriving aircraft, inspect them, and reload them in preparation for a potential strike.
The squadron was tasked with handling conventional munitions and special weapons, which could be either atomic or thermonuclear weapons, according to the report obtained by Masaaki Gabe, a professor emeritus at the University of the Ryukyus, along with other declassified U.S. documents that were shown to Kyodo News.
The report also showed that a number of nuclear components were received by air shipment in January 1957, two months before "Operation 'White Horse'...the most extensive deployment of the (squadron's) aircraft ever to utilize a Far East Air Base as a staging area."
It showed the drills in the first six months of that year involved handling of numerous bombs, including the MK-15 -- a 3.4-ton hydrogen bomb deemed 100 times more powerful than the atomic bomb dropped on Hiroshima.
"Loading personnel completed one of the busiest monthly training schedules of the year in May, accomplishing four MK-6 loadings in an average time of 1:07 hours, 59 MK-15 loadings in an average time of 1:14 hours, and four MK-21 loadings in an average time of 2:10 hours," it said.
In June, six of the eight loading crews were trained in MK-6 MOD-6 atomic weapon loading procedures, stating the personnel of the 12th squadron "finally got ample opportunity to practice loading weapons other than the MK-15 -- and ones which were the most likely to require loading under actual (emergency war plan) conditions," it said.
Gabe pointed out various units and weapons had been sent to the Kadena base in line with changes to U.S. military strategy.
"In the event of a Taiwan Strait contingency, they will make sorties from the air base, which is the closest base to the region," he said.
The 1957 report showed the quality control section of the squadron also had to perform periodic airing and sunning of the stored weapons to cope with high humidity, described as "the worst aspect of Okinawa."
"Rusting, rotting, and corroding, tarnishing, mildewing, and molding, almost nothing is exempt from its influence," it said, adding the exteriors of weapons were very susceptible to deterioration due to humidity.
In addition, it touched on plans involving nuclear weapons stored at Kadena and Iwo Jima managed by the 7th Tactical Depot Squadron, another U.S. Air Force unit whose function included the receipt, storage and loading of special weapons.
Iwo Jima, also known as Iwoto Island, located around 1,200 kilometers south of Tokyo, had been gradually built up as an additional nuclear weapons storage area, despite the heat radiated from its volcanic soil, according to the report.
Okinawa, where around 1,300 nuclear weapons had been deployed by 1967 during the Vietnam War, was returned to Japan in 1972 after the removal of nuclear arms.
Although Japan's nuclear policy prohibits the possession, manufacture and introduction of nuclear weapons in its territory, Tokyo and Washington later made a secret agreement allowing such arms to be brought to Okinawa in a contingency.
The University of the Ryukyus' Research Institute for Islands and Sustainability plans to display the U.S. documents on its website in the near future.