A B-2A Spirit thunders down the aging airstrip of Whiteman Air Force Base and takes off, curving east over the rolling forests of Missouri.
It flies past the empty silos where Minuteman nuclear missiles slumbered through all the long years of the Cold War, past the nation's capital, across the Atlantic Ocean, to where the first of three giant KC-135R Stratotankers it will encounter in the long night waits with fresh fuel.
More than 19 hours later, the bomber slices above the Karkas mountains of central Iran and releases a 4,500-pound "bunker buster" over a complex of buildings guarded by aging missiles and obsolete guns. Explosions echo across the countryside.
[Podcast: James Finefrock and Abbas Milani about the repercussions of an air assault on Iran. ]
[Podcast: Phil Bronstein joins Mick LaSalle and Leba Hertz. ]
That, according to many experts, would be the opening gambit in a war against Iran -- should the United States decide to undertake that risky option.
"Iran has been a focus of war gaming for many years both inside and outside the Pentagon, and I have been around and participated in some of that. I have 'invaded' Iran probably 20 times; I have 'bombed' Iran 30 or 40 times," said Sam Gardiner, a retired Air Force colonel who has taught strategy and military operations at the National War College.
The Bush administration is constantly reiterating its desire for a diplomatic solution to the crisis over Iran's nuclear program. But the administration emphasizes that nothing is "off the table," including military action.
"The evidence is overwhelming that plans have not only been dusted off, but they are at the White House," Gardiner said. "The president believes that he has got to do this."
Other analysts are far more guarded.
"Only the president and a small number of his intelligence advisors can know at this point," said Michael Eisenstadt, director of the Military and Security Studies Program at the Washington Institute for Near East Policy. "I think this could go both ways."
What would a military strike look like?
U.S. military options range from the subtle to the extreme.
Washington could sponsor Iranian dissidents, or employ U.S. Special Forces to conduct covert operations within Iran, sabotaging nuclear facilities or assassinating key scientists. In the view of many analysts, however, such operations, while important as part of any broader military approach, are insufficient to stop Iran's nuclear program.
At the other extreme, the United States could launch a full-scale invasion. That would be enormously demanding -- Iran is much larger and more mountainous than Iraq, and is likely to put up far more resistance.
"Nobody that I know of is talking about the use of ground forces," Gardiner said. "I think the one thing the administration has learned from (the Iraq war) is don't invade."
Between those options are several air-strike scenarios ranging from limited attacks on Iranian military assets or carefully selected research sites to sustained and broad strikes against political, military and scientific targets seeking not only to wipe out Iran's nuclear program but to topple its government.
Analysts consider the latter idea unlikely -- air power alone has not proven effective at toppling governments in the past and such a sustained assault would take months and come at enormous political and diplomatic cost. But some analysts say there is little point in limiting the strikes.
"There's no difference between bombing one site and bombing 1,000 sites, politically," said Andrew Teekell, a security analyst at Stratfor, a private intelligence consultant.
The most likely option, in the view of many experts, is a campaign of air strikes limited in time and breadth, but enough to significantly delay or destroy Iran's nuclear program.
Analysts disagree on the wisdom of such an attack. But there is broad agreement that the U.S. military has the ability to strike nearly at will against the outdated Iranian defense, even if it must do so alone, but there is also agreement that the effectiveness of a bombing campaign is uncertain, and that the possible consequences of such action could be wide-ranging, long lasting and unpleasant.
As such an attack unfolded, Stealth B-2A bombers from the continental United States would be joined by fighters, bombers and missiles from submarines, carriers and cruisers based in the Persian Gulf.
Iranian defenses are outdated -- its air force comprises a few hundred fighters, many of them poorly maintained, including Soviet-era MiG-29s and U.S.-made F-14s that predate the collapse of U.S.-Iran relations three decades ago -- and its arsenal of surface-to-air missiles and anti-aircraft weapons have little chance of overcoming modern U.S. countermeasures.
According to Anthony Cordesman, an analyst with the Center for Strategic and International Studies, Iran has clustered land-based air defense systems -- U.S.-made Improved Hawks dating from the 1970s and Soviet-era SA-2s -- around some obvious targets, such as the uranium enrichment facility at Natanz, south of Tehran, and the heavy-water reactor at Arak, southwest of Tehran.
The Russian-designed reactor being built at Bushehr, along the Persian Gulf coast, is also defended, and would be a risky target because of the several hundred Russian workers there who might be killed. Another hurdle is uncertainty over Iran's nuclear research program -- where it is, how large, and how well it is protected.
Even the known components of Iran's program are widely dispersed, and recent satellite images suggest the Iranians have constructed underground chambers, protecting their equipment with as much as 45 feet of reinforced concrete and dirt.
Those challenges, say military experts, can be surmounted with multiple bombing sorties. But that exposes U.S. pilots and Iranian civilians to greater risk.
It's unclear how many targets U.S. bombs would need to hit, and how often. The International Atomic Energy Agency identified 18 nuclear sites in Iran, but Gardiner and other analysts say new construction has increased the number of necessary "hit points," by Gardiner's count, to about 400 for the nuclear program alone.
"Could very well be 2,000, 2,500, 3,000 after you begin to add in all the other things like air bases, missile storage sites," he said. "The nonnuclear part is expanding." Cordesman estimates the number of sorties by bombers and cruise missiles would range from several hundred over a week's period for strikes focused on nuclear and missile sites to as many as 2,500 over a period of months for wider strikes including those targeting Iran's retaliatory military capability.
Whatever does survive a U.S. attack -- and most analysts suspect some portion of Iran's nuclear program would -- is likely to become the kernel of a new program, said analysts who cited Israel's 1981 destruction of the Osirak reactor, where Iraq responded by vastly increasing investment in its nuclear program, from 400 scientists with a budget of $400 million, to 7,000 scientists with a budget of $10 billion.
There are several ways Iran could retaliate after an attack. Iran could immediately expand the acts it is already accused of doing: using its proxies in the Middle East -- Hezbollah in Lebanon and Shiite militias in Iraq, for example -- to foment violence and instability.
"I don't know how much of a pep talk those groups would need from the Iranians to attack U.S. assets," Teekell said. "They could raise all kinds of hell in Iraq."
Israeli and U.S. forces in several nearby nations are within range of Iran's Shahab-3 missiles, too. Iran already has threatened to attack Israel's nuclear reactor if its own is attacked.
Some analysts foresee post-attack Iran sponsoring acts of terrorism against U.S. interests around the world, and perhaps within the United States itself. But others say Iran would see such acts as too provocative.
That risk might ultimately depend on how hard the United States hits Iran.
"The problem is if you go too high up on the escalation scale ... it starts to look like regime change, and then you've got an enemy who thinks his back is against the wall," Eisenstadt said. "Do we want to put them there? I'm not sure we do."
Perhaps Iran's most effective weapon would be withholding the oil it sells to the rest of the world -- although that has its own risks. Halting sales would be economically self-destructive.
And while Iran might be able to halt the flow of oil from Iraq by sabotaging its pipelines, and the flow from other Gulf nations by blockading the Strait of Hormuz, those steps might do Tehran more harm than good because they would invite renewed U.S. attacks and could tip world sympathy away from Tehran.
"I'm not sure the Iranians want to screw with shipping in the gulf ... that's a two-edged sword for them," Eisenstadt said. But "it may be with 50 billion in cash reserves, they feel willing to live with that for awhile."
A full blockade is probably outside the ability of Iran's Kilo-class diesel submarines and aging navy and air force to pull off. But threatening traffic in the straits is well within Iran's means, many analysts say, and could serve its economic interests as well.
Iran could harass vessel traffic by laying mines from commercial vessels that would not be easily traced to Tehran -- either by using proximity mines that some reports suggest may already be lurking on the bed of the strait, or by using speedy C-14 catamarans armed with machine guns, anti-ship missiles or suicide bombers to assault oil tankers.
Exactly how much harm such harassing attacks could do is uncertain. But given the jittery nature of world oil markets and insurance companies, even the threat of such attacks could send oil prices to record highs, severely harming the U.S. economy.
Should the oil flow be completely cut off -- two-fifths of the world's oil, from various gulf countries, passes through the strait -- the United States could use military force to keep the Strait of Hormuz secure, but that action could quickly escalate.
"Either we're going to lose oil flow through the straits, or we're going to send ground forces into southern Iran," said Richard Andres, a professor at the Air Force School of Advanced Air and Space Studies. "All of a sudden, what you've got is ground forces occupying southern Iran, which is the worst thing in the world."
The U.S. could try to invade Tehran and install a new government, much as it did in Iraq. But Iran is several times larger than Iraq, has a more-complicated terrain and a population analysts say is more likely to unite and fight against an invading force.
The grim features of each option facing the United States if it chooses to fight leave many analysts arguing that there is no military solution to the Iran crisis.
"Unless the U.S. does find evidence of an imminent Iranian threat -- which at this point might well require Iran to find some outside source of nuclear weapons or weapons-grade material -- the U.S. may well simply choose to wait," Cordesman wrote. "Patience is not always a virtue, but it has never been labeled a mortal sin."
Others argue that our disavowing the threat of force now might have a counterintuitive effect: It might actually weaken Iran's bargaining position.
"The threat of war plays right into the hands of Iranian hard-liners and encourages the ultranationalism that helps drive nuclear ambitions. There are plenty of other carrots and sticks to offer," said Stephen Zunes, a professor of politics and international studies at the University of San Francisco. "If the only thing in your toolbox is a hammer, pretty soon everything starts looking like a nail."
Nevertheless, some analysts who oppose an attack say diplomacy works best when both sticks and carrots are in plain sight.
"You have to wed diplomacy with the threat of force
-- with the credible use of force -- to get the Iranians to negotiate,"
said Richard Russell, professor of national security affairs at
National Defense University. "Absent that credible threat of force, I
think what you have is just Iranian charades."
A U.S. attack on Iran’s nuclear research program could involve B-2A Spirit bombers, shown above, employing precision munitions such as the 5,000-pound GBU-37 "bunker buster" or other, even heavier weapons still under development. The stealth bombers would be supported by fighters, bombers, and aircraft for refueling and rescue. Submarines, cruisers and destroyers could also launch Tomahawk cruise missiles against Iranian targets, seeking to reduce Iran’s ability for defense or retribution.
Guided Bomb Unit-37 (GBU-37)
"Bunker Buster"
BODY -- 4,000-pound modified artillery tube.
COST -- $231,250 per unit
RANGE -- More than 5 nautical miles
WARHEAD -- 630 pounds of explosive. A mixture of TNT and aluminum powder speeds up the maximum pressure of the explosion. This mix makes it 18 percent more powerful than TNT alone.
GPS GUIDANCE SYSTEM -- Uses a satellite-based Global
Positioning System instead of placing laser markers on targets for
typical navigation system.
Iran's military punch
Iran's ability to defend itself against U.S. air strikes is limited by its equipment, much of which is decades old.
.
Surface to air missiles:
-- U.S.-made improved Hawk systems
-- Soviet and Chinese SA-2s, SA-
-- Russian SA-6s
-- British Rapiers
Man-portable systems:
-- SA-7s and SA-14s
In addition, Iran has several thousand anti-aircraft guns and an aging air force of several hundred planes "many believed to be nonfunctional, " including American-made F-14s and Soviet MiGs. Most of those systems, according to analysts, are outmatched by U.S. countermeasures.
Persian Gulf retaliation: Iran can retaliate after
U.S. air strikes through conventional means, such as launching its
Shahab-3 missiles at U.S. targets in the region, and through
unconventional means, such as using proxy terrorist groups like
Hezbollah. In addition, Iran could target the Strait of Hormuz, a
critical path for the world’s oil, by using anti-ship missiles
positioned along the shore, Kilo-class diesel submarines, by placing
mines in the strait or by attacking ships using Chinese C-14 Cat-class
catamarans equipped with machine guns, anti-ship missiles or suicide
bombers.
Population: 68.7 million
Growth rate: 1.1%
Median age: 24.8 years old
Life expectancy: 70.3 years old
Shiite Muslim: 89%
Sunni Muslim: 9%
Zoroastrian, Jewish, Christian and Baha’i: 2%
GDP: $181.2 billion
Labor force: 23.7 million
Unemployment rate: 11.2%
Population below poverty line: 40%
Telephones: 11.2% of population
Landlines: 14.6 million
Cellular: 4.3 million
Internet users: 7.5 million
Production Millions of barrels per day
Saudi Arabia - 9.5
Russia - 9.2
United States - 7.6
Iran - 4.0
China European - 3.5
Union - 3.4
Mexico - 3.4
Saudi Arabia - 262.7
Canada - 178.9
Iran - 133.3
Iraq - 112.5
United Arab Emirates - 97.8
Kuwait - 96.5
Venezuela - 75.6
E-mail Matthew B. Stannard at mstannard@sfchronicle.com.