HAGATNA, Guam — People on this faraway island — a U.S. territory 3,800 miles west of Hawai'i — delight in calling Guam the "tip of the spear" for its role defending U.S. interests in the Far East.

The Pentagon has chosen Guam, a quirkily American place that marries the beauty of Bali with the banality of Kmart, as the prime location in the western Pacific for projecting U.S. military muscle.

Guam has served as an important U.S. military outpost since World War II. But now the sultry tropical island, a bit smaller than Moloka'i and with a population of 173,000, is set to become a rapid-response platform for problems ranging from pirates to terrorists to tsunamis, as well as a highly visible reminder to China that the United States is nearby and watching.

To that end, U.S. Marines by the thousands and U.S. tax dollars by the billions ($13 billion at last count) are to be dispatched to Guam over the next six years, along with a major-league military kit that includes Trident submarines, a ballistic missile task force, Navy Special Operations forces and Air Force F-22 fighter jets. Nuclear-powered attack submarines and B-2 stealth bombers have already arrived, and preparations are being made to accommodate aircraft carriers.

The peacetime invasion, due to continue into 2014, will balloon the island's population by about 40,000 service people, contract workers and dependents, an increase of almost 25 percent. Real estate prices have jumped, and outside investors are descending on the island. A Chamber of Commerce poll found widespread popular support for the move.

"We can't help but boom," said Jeff Pleadwell, who owns Jeff's Pirates Cove, a beach hamburger joint, and expects his business to prosper. "But the island is going to change radically. Everyone is scared — of how the Marines will behave. We also worry that life inside the base will be first-world, while outside the fence it is going to be third-world."

GUAMANIANS JITTERY

All in all, the Marine move is giving many Guamanians — an extraordinarily patriotic people who fight and die in U.S. wars at rates much higher than on the Mainland — a serious case of the jitters.

"We are proud to be the tip of the spear, but the federal government needs to assist us to make sure that the quality of life outside the military fence line is better, not worse, after the Marines come," said Michael Cruz, lieutenant governor of Guam, a colonel in the Guam Army National Guard who has served in Iraq and a point man in local planning for the Marine move.

Whether or not that assistance materializes, the plan is proceeding. The Marines are moving here from Okinawa, Japan, where their six-decade presence has sometimes outraged the local people. The Japanese government, as part of a unique joint security deal with the United States, is footing $6.1 billion of the cost for housing the Marines on Guam.

The U.S. federal government already owns about a third of the island, and military planners here say they may buy or lease still more so Marines can train with rifles, mortars and heavy machine guns.

The newcomers will be mostly young, mostly single men trained as warriors — and periodically looking for a big night out on a small island where most hotels and restaurants cater to the sushi-and-kimchi predilections of upper-middle-class Japanese and South Korean tourists.

"The military wants to have a pool party, but they are telling us to build the pool," said James Espaldon, a Guam senator who oversees the island's infrastructure.

ECONOMIC MORASS

Even before the Marines were coming, the debt-ridden government here struggled — and in many cases failed — to maintain roads, water lines, schools and a balanced budget. The island's landfill is bursting at the seams with garbage and is in violation of federal environmental laws.

It doesn't help that the island sits in an area of the Pacific known as Typhoon Alley and is regularly pummeled by storms that flatten nearly everything not made of reinforced concrete. Guam is also near a major geologic fault and has been hit by major earthquakes, most recently in 2001.

The newcomers could bring on an infrastructure breakdown unless the federal government comes up with "significant funding," the U.S. Government Accountability Office said in a study published in September.

Guam's government says it needs $2 billion to $3 billion in federal funds to cover outside-the-fence costs of the military move. The Pentagon, with its patronage and lobbying links to the key members of Congress who dole out money, can be fairly sure it will get its $13 billion for the inside-the-fence part of the buildup, but the Guam government is assured of nothing.

The Defense Department is neither authorized nor obligated to compensate Guam for the whole of the long-term impact of the Marines' presence on the island, according to retired Marine Maj. Gen. David Bice, executive director of the Joint Guam Program Office, which is managing the Pentagon's move.

Bice said, though, that the Pentagon recognizes that Guam's needs are real and extensive: "The federal government is recognizing that this has to be a move that is good for the people of Guam."

Several federal agencies have created a Guam task force and have held two meetings in Washington to try to find money for the island. But like the District of Columbia, Guam has no votes in Congress. And unlike the District, which sits where power and the news media sit, Guam is halfway around the world.

"Most people think we are in Central America," said retired Army Col. Dennis J. Santo Tomas, an adviser to Guam on homeland security matters.

Military planners in Washington, speaking on condition of anonymity, predicted that Guam would have trouble securing the money it will need for coping with the military buildup.

Here on the island, elected officials are expressing growing concern. "Look, no jurisdiction in the States would tolerate such a big buildup in such a short time," said Cruz, the lieutenant governor. "This growth has to be balanced — inside the fence and outside."

Guam does have an ace up its sleeve when it comes to paying for the cost of the newcomers. Under federal law, income taxes paid by all residents on the island — including those serving in the military — must remain on Guam. Instead of going to the U.S. Treasury, they flow into the island's general operating fund.

Tax revenue from 40,000 new residents would be a substantial windfall, perhaps as much as $200 million (the island's current tax revenue is about $500 million). But the new money will not arrive until well after the taxpayers do — and well after Guam will have to start improving its port and roads and expanding its schools.

Nearly everyone planning for the Marines' arrival worries about this Catch-22. But so far there are no solid plans for bridge loans or bonds to solve it, said Bertha Duenas, Guam's acting budget director.

MISBEHAVIOR FEARED

There is another major local worry: How will those young Marines pass their off-duty hours?

On Okinawa, three U.S. servicemen — a sailor and two Marines — were convicted in 1996 of kidnapping and raping a 12-year-old Japanese girl. The crime triggered months of anti-military protests on Okinawa. "What happened there is not at all lost on us," Cruz said.

To lessen chances of conflicts with local people, the Guam government has asked the military to hold special courses in "how to behave" before the Marines arrive and to periodically conduct refresher courses.

In Washington, Bice, who is directing the move to Guam, bristled at the suggestion, saying that he "challenged anyone to find a more disciplined, more goal-oriented group of young people" than Marines. "There will be cultural-awareness training for individuals who arrive on Guam," he said, "just as there is training anyplace we assign military men and women."