NAHA -- A spate of accidents and mishaps involving U.S. military helicopters in Okinawa Prefecture seems to signal that the tense situation surrounding North Korea's nuclear and missile development is putting a severe strain on U.S. forces stationed in Japan.
Defense budget cuts during the Barack Obama administration may also be a factor behind the problems plaguing the U.S. military.
There have already been two emergency landings by U.S. Marines helicopters in Okinawa since the beginning of this year.
These incidents came on the heels of an accident in late December, in which a window from a U.S. military transport helicopter fell onto the grounds of an elementary school in Japan's southernmost prefecture, where a large portion of the U.S. military bases in Japan are located.
"I am speechless," said Okinawa Gov. Takeshi Onaga on Tuesday after an AH-1 attack helicopter made an emergency landing in Yomitan, a village in the prefecture, on Monday. "People in the prefecture are exposed to danger."
Two days earlier, a U.S. Marine Corps UH-1 helicopter made an emergency landing on Ikei Island in the prefecture.
A top officer of the U.S. military in Okinawa described the spate of incidents as "crazy" to a senior official of the prefectural government.
Both of the helicopters that recently made forced landings are based at the U.S. Marine Corps Air Station Futenma in the city of Ginowan.
In December, a window fell from a CH-53E helicopter deployed at the same air base onto the playground of an elementary school close to the base.
Shortly before the accident, another component from a U.S. military aircraft was discovered on the roof of a nursery school in Ginowan. It is believed to have come from a CH-53E helicopter.
No increase in accidents
Despite the recent rash of incidents, however, there has been no significant increase in the number of accidents involving U.S. military aircraft in Okinawa Prefecture. About 30 such accidents were reported in 2017, a figure not markedly larger than usual.
But the recent string of incidents have all occurred in residential areas, raising concerns among people in the prefecture that there may be some structural problems behind them.
On Tuesday, Defense Minister Itsunori Onodera made a telephone call to U.S. Defense Secretary James Mattis and asked him to take effective steps to prevent a recurrence.
Mattis reportedly said he was sufficiently aware of the situation and promised to tackle the problem as a policy priority.
Foreign Minister Taro Kono lodged a protest with U.S. Ambassador to Japan William Hagerty.
Budget woes may be a factor behind the rash of troubles that have involved U.S. military aircraft in Okinawa.
In October, the Heritage Foundation, a conservative think tank in Washington, warned about the problem in its annual assessment report on the capabilities of the U.S. military. Due to shortages of components and manpower caused by budgetary restrictions, "only 41% of the Marine Corps fixed-wing and rotary-wing aircraft were considered flyable," according to the foundation's report.
Some experts say the defense budget curtailments during the Obama administration are affecting the U.S. military's operations.
Referring to a delay in the program to replace the Marine Corps' CH-53E, which entered service in 1981, the report said the Corps "will not have enough helicopters to meet its heavy-lift requirement without the transition to the CH-53K," the successor to the CH-53E.
The new helicopter is predicted to reach initial operating capability in 2019, "almost four years later than initially anticipated," the report said.
The Marine Corps is expecting full operational capability of the CH-53K in 2029.
The Okinawa prefectural government said the series of accidents have been caused by such factors as aging of the fleet, overworked personnel and excessive exercises.
After the accident involving the falling helicopter window in December, the prefectural government demanded that all U.S. military aircraft in Okinawa be grounded for fresh inspections. But flight operations resumed after safety checks only on the CH-53Es.
After that, the emergency landing incidents involving other types of U.S. military helicopters took place.
Korean Peninsula strains
A heightened level of U.S. military operations in response to the crisis in the Korean Peninsula may be an additional cause behind the incidents.
Following a series of collisions involving the U.S. Navy's Aegis destroyers in 2017, experts pointed out the increased burden on the Navy due to operations related to North Korea.
There have also been a flurry of U.S. military moves in Okinawa linked to the situation in the Korean Peninsula.
In November, a fleet of advanced F-35A stealth fighter jets was deployed to Okinawa's Kadena Air Base.
The fighters have since been conducting drills with other aircraft, including the B-1 strategic bomber.
Lt. Gen. Lawrence Nicholson, the top commander of U.S. military forces in Okinawa, has said a lot of time is being spent on exercises focused on South Korea.
Currently, various U.S. military units frequently travel between South Korea and Okinawa.
The increased level of U.S. military operations in Okinawa has been confirmed by a sharp rise in noise levels around U.S. bases in the prefecture.
Despite a bilateral agreement on restrictions on flight operations between 10 p.m. and early morning, as of end of November, there were 25 average monthly cases of noise from U.S. military aircraft during those hours in fiscal 2017 at three key observation locations, double the level two years earlier.
The U.S. military does not disclose details of its operations. But it may have been conducting more practical exercises in other camps within the prefecture.
In recent years, noise related to U.S. military operations in Okinawa reached the highest level in 2003, when the U.S. launched its war against Iraq. U.S. Marines stationed in Okinawa took part in those operations.
Immediately after the war started, a U.S. Marine Corp's CH-53D heavy-lift transport helicopter, stationed at Futenma, crashed on the campus of Okinawa International University in Ginowan. The helicopter was the predecessor of the CH-53E.
Since the December window accident involved a CH-53E occurred amid growing tensions in the Korean Peninsula, it reminded many people in Okinawa of the 2003 accident.
Gov. Onaga has criticized the U.S. military for conducting frequent drills in response to the situation linked to North Korea's nuclear and missile developments amid serious shortages of money and components.
A Japanese government source said Tokyo is watching closely how the tensions in the Korean Peninsula, which will continue for the time being, will affect the operations of the U.S. military.