If US officials had been hoping to quell anti-base sentiment in Japan, the arrival in the country this week of the first shipment of Osprey transport aircraft could not have been worse timed.
The tilt-rotor aircraft are soon to replace aging CH-46 helicopters at Futenma, a marine corps base on the island of Okinawa that has come to symbolize Washington's struggle to reconcile security with public opinion overseas.
Under a bilateral agreement reached in 2006, Futenma, located in the middle of a densely populated city, was to have been moved to Nago, a more secluded location on the island's coast, only for the move to fail amid opposition from people living near the proposed new site.
Having failed to find an alternative location, officials in Japan and the US have had to concede defeat. The Futenma base will stay put, at least for the time being.
No one is happy with the diplomatic fudge that followed. Not the people of Nago, who still fear their unspoiled coastline will eventually make way for a new runway; not the Pentagon, which sees the relocation as essential to its troop realignment plans; and not the Japanese government, now stranded in a political limbo between its chief ally and disgruntled voters at home.
The Okinawa conundrum has been complicated by the recent arrival of 12 MV-22 Osprey aircraft at Iwakuni marine base in western Japan, where they were greeted by a sit-in protest and complaints from the local mayor.
Those demonstrations are like to be dwarfed when the assembled aircraft are taken to Futenma in September.
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To the Americans, the Osprey fleet is vital to the modernization of its military capability in a region where Chinese naval maneuvers and tensions between North and South Korea are a constant source of anxiety.
"Deployment of these aircraft in Japan is a vital component in fulfilling the United States' commitment to provide for the defense of Japan and to help maintain peace and security in the Asia-Pacific region," the US embassy in Tokyo said in a statement.
At the heart of local opposition are nagging doubts about the Osprey's safety record. The aircraft, which can take off and land like a helicopter, has seen extensive service in Iraq and Afghanistan. They carry bigger payloads than the CH-46.
But they have also been involved in recent accidents in Morocco and Florida. At least one expert has questioned the plane's safety, particularly when flown in formation at slow speeds.
"There are lots of opportunities for the pilot to make a little mistake. And, if you make a mistake in a V-22, you crash," Rex Rivolo, a former chief analyst at the US Institute for Defense Anlayses, said in an interview with Kyodo News.
Supporters of the deployment point out that that replacing the CH-46 transport helicopters, which have been in service for more than 40 years, is long overdue. In addition, the rate of serious accidents – those resulting in death or damage worth $2 million US or more – involving the Osprey is lower than that of any other type of aircraft used by the US Marines.
But it is only a matter of time, opponents in Okinawa say, before one of them plunges into a populated area near Futenma, or falling parts land on one of the dozens of schools, hospitals and shops surrounding the base.
A nearby university was the scene of a crash involving a CH-53 helicopter in 2004, and islanders remember the day in 1959 a US fighter jet plowed into an elementary school in central Okinawa, killing 17 people, including 11 children.
The Ospreys' imminent deployment has added to the diplomatic challenges facing Japan's unpopular prime minister, Yoshihiko Noda.
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He had hoped to buy time time with a recent agreement to move about 9,000 marines and their families off Okinawa – regardless of the Futenma base's future – thereby reducing the burden on an island that hosts about half the 50,000 US troops stationed in Japan.
Now he has to explain why an aircraft that has raised legitimate questions over its safety will be sent to a base that the US and Japan have already agreed should be closed, partly because of the dangers faced by the local population.
Noda has said that none of the Ospreys will be permitted to fly until investigations into the Florida and Morocco crashes, which killed two airmen and injured five others, have been completed.
US documents quoted by Japanese media show that Osprey were involved in 58 incidents in a five-year period from 2006, although the Japanese government did not disclose the transport aircraft's complete safety record prior to its arrival in Iwakuni.
Noda has asked senior US officials to provide safety assurances before the Ospreys can conduct test flights around Iwakuni in late August. While Washington has agreed to share that information, it has shown no inclination to rethink the deployment.
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Few are convinced that Noda has the backbone to alienate the US further by keeping Ospreys grounded after they are due to go fully operational in Okinawa in early October. "The deployment itself is a basic policy of the US government," he told Japanese TV earlier this month. "Although Japan is an ally of the US, this isn't the kind of situation in which we tell the US government what to do."
The Japanese media have likened Noda's reassurances to those he made over the restart of a nuclear reactor last month — a move that contributed to a dramatic fall in his approval rating. One newspaper said that in agreeing to the deployment on simple security grounds, he sounded "like a middle manager who does everything his boss tells him to do."
Local governments in other parts of Japan have called for more information on the planes' expected flight paths, which won't be limited to Okinawa. "We cannot accept [the planned deployment of the Osprey] since their safety has yet to be confirmed, despite the anxieties of local governments and residents," prefectural governors said in a resolution.
Seiji Maehara, policy chief of the ruling Democratic Party of Japan, has warned that an accident could do "major harm" to US-Japan relations. Noda's task in the coming weeks will be to limit the damage that his support for the Osprey deployment could inflict on his already fragile administration.