YOMITAN, Okinawa -- Among the lush jungle and dazzling sand beaches of this island, 30,000 Americans serve on military bases, waiting for the enemy to strike.
But who is the enemy? And where?
Answers do not come as easily as they once did. And so one of the questions for U.S. foreign policy in coming years will be whether to maintain 63,000 Americans at 94 military sites in Japan.
For now, the U.S. and Japanese governments agree that the U.S. bases are essential for maintaining peace in Asia. But some voices suggest it is time the troops went home.
The stakes could scarcely be greater. If supporters of the bases are right, closing them could promote arms races in Asia, encourage Japan to develop a powerful army with nuclear weapons, embolden China to be the regional bully and provoke devastating new wars.
"In my lifetime, the three major wars all started out here," said Walter F. Mondale, the U.S. ambassador to Japan. "We're trying to do it differently this time."
Mr. Mondale, whose background as vice president and Democratic presidential candidate was anything but hawkish, says he becomes more convinced daily of the need to maintain U.S. troops in Japan.
But Chalmers Johnson, an American scholar of Japan, argues that the U.S. military presence in East Asia is wasteful and actually increases the risk of war.
"It's an accident just waiting to happen," said Mr. Johnson, who calls for cutbacks in the current issue of Foreign Affairs.
The debate about the U.S. military presence seems much more immediate here on the southern Japanese island where Americans and Japanese hurled grenades at each other 50 years ago.
U.S. bases occupy 20 percent of the island, and polls show that at least two-thirds of Okinawans want the bases closed.
U.S. paratroopers get a sense of the local mood whenever they practice here at Yomitan air field. Dozens of local people gather around the outside of the target field and detain any soldier who misses and lands on someone's front lawn.
So there are undignified episodes in which an errant paratrooper rushes back to the base pursued by angry retirees.
"For 50 years we have been under de facto rule by Americans," complained Masaaki Aguni, director of Okinawa's military base affairs office. His objections are practical, not ideological: The war planes make thunderous noise, the bases take up valuable farmland, the live artillery exercises -- over a public highway -- are dangerous.
The Japanese as a whole, however, appear to support the U.S. military presence. Polls have consistently found that more than 60 percent of those surveyed support the current security arrangements.
The Clinton administration also is intent on maintaining a strong troop presence in Japan.
When Col. Robert McEneany of Kadena Air Base in Okinawa was asked to cite reasons why U.S. forces are necessary, he did not pause.
"What about the runaway rearming of Japan?" he asked. "If we had left after the Korean War, who knows? Japan might have rearmed and gotten nuclear weapons."
That thought terrifies Asia, which was traumatized by Japan's brutal rule of Korea and wartime invasions from China to Indonesia.
Lee Kuan Yew, the senior minister of Singapore, expressed the region's mood when he said that allowing Japan to send troops abroad would be "like giving a chocolate liqueur to an alcoholic."
The administration also is concerned about Russia's directions and, particularly, the rise of China's military, the world's largest army, with 3 million troops, and perhaps the fastest-growing budget.
Supporters of the bases believe they are all the more important these days since the closing of Clark air field and Subic Bay naval base in the Philippines in 1992.