Old-Fashioned Hide-Outs Fuel High-Tech Weaponry

The power of the U.S. military was on dazzling display on the first night of the 1999 war in Yugoslavia, when a single B-2 bomber wiped out all the Serbian military planes at the Pristina airport in Kosovo.

But the limits of American might were demonstrated near the same airport on the final day of the war. With the threat of attack lifted, Serbian troops threw open the doors of a hangar dug beneath a mountain, then looked on with satisfaction as scores of unscathed MIG fighters roared into flight.

The planes were beyond the reach of all the bombs and missiles in the U.S. arsenal. Their survival illustrates why a growing number of countries are burying their most precious military assets--and why the Pentagon is racing to build weapons powerful enough to reach them.

The urgency of this contest became clear last week, with the disclosure of a secret Pentagon report calling for the United States to take the controversial step of developing small nuclear weapons suited to this bunker-buster mission. The report said that America’s most worrisome potential adversaries are moving their weapons underground, and acknowledged that “at present, the United States lacks adequate means to deal with these facilities.”

The report quickly touched off a worldwide debate among foreign governments, lawmakers and arms experts. At issue are whether such “mini nukes” could be used effectively without endangering civilian populations, and whether such smaller weapons would make it more likely that the United States and other countries would actually use them.

The trend of the world’s militaries migrating underground poses one of the gravest challenges faced by the Pentagon.

“We’ve been reaching a point where the conventional weapons are not good enough against an opponent who has the time and money to build things underground,” said Robert Hewson, editor of Jane’s Air-Launched Weapons publication.

U.S. bomber aircraft have been trying to find and destroy underground facilities since World War II, when Germany’s Adolf Hitler sought to conceal his V-2 rockets in shelters. During the Cold War, U.S. and Soviet planners fretted about how to preserve their missiles and leaders underground during a nuclear war--a worry lampooned in the movie “Dr. Strangelove” as a “mine-shaft gap.”

But U.S. anxieties have deepened in recent years, as world leaders have become convinced that the recesses of the Earth are one of the last places beyond the reach of U.S. arms.

The Pentagon’s Nuclear Posture Review said there are an estimated 10,000 underground facilities in 70 countries. About 1,400 sites are considered “strategic” because they house leadership bunkers, missiles and facilities for manufacture and storage of chemical, biological and nuclear weapons, it said.

That number has increased by more than one-third just since 1998, the report said.

These underground complexes can cover acres, and many are equipped to garrison hundreds of troops for months. They are often protected by surface-to-air missiles and have multiple ventilation, communications and power systems so they can still operate if part of their equipment is damaged in an attack.

Among the most dedicated builders of underground facilities are the North Koreans, who have hollowed out granite mountains near the demilitarized zone to conceal planes, tanks, troops and artillery that could cross the border in an attack.

They also have become popular in the Middle East and are widely used by the Iraqis, who are believed to be hiding chemical and biological weapons. The Russians continue to maintain vast underground facilities. Even in the late 1990s, with a shrinking military budget, U.S. intelligence believed the Russians were spending billions on a huge underground facility in the Urals called Yamantau Mountain.

The United States has its own large network built during the Cold War, including several in the Washington area designed to protect national leaders. Among them are Mt. Weather in western Virginia and Raven Rock near the Maryland-Pennsylvania border.

With the threat from Russian missiles declining, authorities have mothballed many of these old facilities. But others still are in use, including the U.S. Space Command’s nuclear-hardened Cheyenne Mountain, near Colorado Springs, Colo., and the U.S. Strategic Command center beneath Offutt Air Force Base in Nebraska, where President Bush flew Sept. 11.

Concern about such foreign facilities grew during the Persian Gulf War, when U.S. forces struggled to improvise new conventional weapons and techniques to get at Iraqi President Saddam Hussein’s underground sanctuaries.

That war saw the debut of the laser-guided bunker-buster, called the GBU-28. The 4,700-pound bomb was built out of 8-inch Army gun tube--a casing that gave the bomb the weight and durability to punch through 100 feet of earth. The bomb was used to destroy an important bunker north of Baghdad protected by 30 feet of earth, concrete and hardened steel.

The attacks of Sept. 11 have brought new impetus for developing more bunker-busters with heavier, slimmer casings and fuses that explode at just the right moment. With new worries about the chemical, germ and nuclear weapons that may be hidden underground, U.S. officials have been accelerating existing programs and scouring defense labs for other promising ideas.

In Afghanistan, the military introduced a “thermobaric” weapon designed to destroy equipment and kill people in tunnels hundreds of yards away from the detonation. Called the BLU-118, the bomb involves two explosions. The first sprays out a powdered chemical and the second ignites it, releasing tremendous heat and a high-pressure wave that scorches and crushes targets at some distance.

Military planners hope the weapon can kill any live germ weapons that might be released from underground storage tanks in an attack.

Despite these and other improvements in conventional arms, U.S. officials still are worried because it is easier for America’s adversaries to dig deeper than it is for the Pentagon to develop weapons that can reach those depths, Jane’s Hewson said.

A key problem is that destroying bunkers requires the kind of precise intelligence that usually is hard to come by. With spy satellites and other sources, general locations of such facilities often can be found. Intelligence officials can draw certain conclusions about the design of the installations from how many people they see coming and going, and how much earth is being trucked away, for example.

But it’s much harder from above-ground surveillance to pinpoint important sections of the facility. Underground tunnels leading from entrances to the bunkers are often long and tortuous.

The Pentagon report said that, without such intelligence, U.S. conventional weapons generally can only disrupt the functioning of underground facilities by severing power lines near the surface or blasting the entrances.

Advocates of using nuclear weapons argue that the nuclear blast and fireball would provide extra power to reach and incinerate unconventional weapons stored underground.

The only nuclear weapon now in inventory for this purpose is the B61-11, and its effectiveness is in doubt. Introduced in 1997, the bomb has a pointed nose made of hard depleted uranium that is supposed to give it extra power to penetrate the ground.

In tests in Alaska, the bomb was dropped from 40,000 feet, yet penetrated only 20 feet into the earth, analysts say. The Pentagon report acknowledges the weapon has problems.

But officials insist the B61-11 holds out hope for other nuclear penetration bombs, pointing out that, with a more effective design, buried targets could be attacked using a smaller weapon than would be required for a nuclear strike on the surface.

Advocates for using nuclear bunker-busters argue that, if an enemy regime killed thousands of Americans with a chemical or biological weapon, a U.S. president might feel justified in using a nuclear weapon to try to obliterate the enemy’s remaining weapon supplies. They also contend that the nuclear weapons in the current U.S. inventory are so large and destructive as to make their use unthinkable in most circumstances, and that only by developing smaller weapons can the U.S. deter potential adversaries.

The flip side of that coin is that, by developing such arms, the United States might foster the worldview that nuclear weapons are acceptable tools.

For that very reason, Congress eight years ago banned U.S. labs from conducting research and development of a bomb smaller than 5 kilotons, lest it “blur the distinction between nuclear and conventional arms.”

Arms control advocates also argue that a nuclear bunker-buster, even one that reached depths of 100 feet, would inevitably spew radiation that would devastate the surrounding area.

Robert D. Nelson, a Princeton University physicist associated with the pro-arms control group Federation of American Scientists, contended in a report last year that “no earth-burrowing missile can penetrate deep enough into the earth to contain an explosion with a nuclear yield even as small as 1% of the 15-kiloton Hiroshima weapon.”

Such an explosion “simply blows out a massive crater of radioactive dirt, which rains down on the local region an especially intense and deadly fallout,” he wrote.

Some analysts question whether anyone could develop nuclear arms mechanisms robust enough to explode only after plowing through yards of rock and concrete.

Even so, advocates believe this new generation of weapons is not out of the question.