As the negotiations between Iran and the P5+1 powers over Tehran's nuclear program near their end, those dedicated to killing a deal potential deal are out in force. The cable news networks are littered with TV ads by United Against a Nuclear Iran (UANI), a group funded in large part by the right-wing billionaire Sheldon Adelson. Online, Secure America Now has turned to Twitter and even Israeli sites like Haaretz to warn a nuclear deal means a nuclear Iran.
But aside from the Los Angeles Times, Vox and Foreign Affairs, there is very little discussion about what will happen if the talks in Vienna break down. (As Zach Beauchamp summed it up in Vox, "If the Iran talks fail, we won't just revert to the status quo. It'll be worse.") Instead, outlets like CNN and Time breathlessly report headlines like "Bunker-Busting Bomb on Standby as Iran Nuclear Talks Near End" and "U.S. Air Force Primed and Ready to Attack Iran's Nuclear Sites." The only question, Time's Mark Thompson said of the Air Force's $15 million, 15 ton Massive Ordnance Penetrator (MOP) designed to destroy hardened, underground facilities like the nuclear installation at Fordow, is "will Obama order it to drop the Big One?"

After several upgrades, the Air Force has let it been known that there's an operational stockpile of the world's most powerful non-nuclear bombs at Whiteman Air Force Base, Missouri. They're not far from the B-2 bombers, ready to carry them 7,000 miles to Iran. That much is certain. Whether Obama thinks dropping them is worth the risk isn't.

But missing from these fawning assessments of using America's most powerful non-nuclear weapon is a much more important question: what happens next? While the usual suspects like John Bolton, Joshua Muravchik and Arkansas GOP Senator Tom Cotton claim the Tehran's nuclear aspirations can be neutralized by "several days of air and naval bombing," most of the American national security leadership vehemently disagree. To ensure that Iran can never develop nuclear weapons, the possible price tag in blood and treasure for an American invasion and occupation of Iran would require "a commitment of resources and personnel greater than what the U.S. has expended over the past 10 years in the Iraq and Afghanistan wars combined."
Here's why, rather than eliminating a future nuclear threat from Iran, a preventive U.S. military strike could produce "the worst of all worlds."
In 2003, General David Petraeus asked of the looming invasion of Iraq, "Tell me how this ends." Twelve years later, the answer remains elusive about a conflict that in comparison to Iran was a comparative cake-walk.
Iran, after all, is far larger than Iraq. With nearly 80 million people, the country has triple the population of its Shiite majority neighbor. According to the Global Firepower Index, the conventional Iranian military counts some 545,000 frontline personnel and 1.8 million reservists, along with about 2,000 tanks and self-propelled guns. (Those numbers exclude the Basij volunteer paramilitaries, who died by the tens of thousands during the Iraq-Iran war and who cracked down on pro-democracy demonstrators in 2009.) Its surface fleet and aging 470 aircraft don't pose a serious challenge to U.S air and naval forces in the Persian Gulf and throughout the region. But it is Tehran's asymmetric warfare capabilities that pose the real problem for American forces. Hundreds of small attack boats and mines, along with more modern anti-ship missiles, could inflict casualties among U.S. ships in the tight quarters of the Straits of Hormuz. Tehran's Quds Forces and Revolutionary Guards have helped train and lead Shiite militia in Iraq, Hezbollah fighters in Lebanon and Syria, and carry out terror operations as far afield as Saudi Arabia and Argentina. Whether attacked by Israel, the United States or both, Iran would almost surely strike back with what long-range missiles it possesses as well with its proxy forces in Gaza and Lebanon.
In January 2008, a confrontation between a handful of Iranian patrol boats and U.S. ships provided in miniature a preview of a future conflict for American commanders. As the New York Times recalled, the episode recalled the outcome of $250 million war game simulation which did not end well for the U.S.:

In the days since the encounter with five Iranian patrol boats in the Strait of Hormuz, American officers have acknowledged that they have been studying anew the lessons from a startling simulation conducted in August 2002. In that war game, the Blue Team navy, representing the United States, lost 16 major warships -- an aircraft carrier, cruisers and amphibious vessels -- when they were sunk to the bottom of the Persian Gulf in an attack that included swarming tactics by enemy speedboats.
"The sheer numbers involved overloaded their ability, both mentally and electronically, to handle the attack," said Lt. Gen. Paul K. Van Riper, a retired Marine Corps officer who served in the war game as commander of a Red Team force representing an unnamed Persian Gulf military. "The whole thing was over in 5, maybe 10 minutes."

Still, many of the Obama administration's opponents in the U.S. and Israel casually brush off Iranian capabilities and Tehran's likely response to supposed surgical strikes designed to cripple its nuclear infrastructure. As Bolton put it, "The inconvenient truth is that only military action like Israel's 1981 attack on Saddam Hussein's Osirak reactor in Iraq or its 2007 destruction of a Syrian reactor, designed and built by North Korea, can accomplish what is required. Time is terribly short, but a strike can still succeed."
But the Iranian scenario is altogether different from the Israeli raids on Osirak and the Syrian reactor. Neither Saddam Hussein (then an American ally) nor Bashar Al-Assad posed a serious threat of military retaliation to the one-off Israeli strikes. Crippling Tehran's nuclear capability would require a sustained military campaign that, short of total invasion and occupation, would only temporarily delay the Iranian program.
That's the precisely the point that Defense Secretary Ashton Carter and Join Chiefs Chairman Martin Dempsey made clear this week. Carter, the Los Angeles Times reported, "sought to downplay the likelihood or the utility of an attack" because "no plan under consideration, including use of the bunker-busters, could deliver a permanent knockout blow to Iran's nuclear infrastructure and enrichment plants."

"A military strike of that kind is a setback, but it doesn't prevent the reconstitution over time," he said. "And that basically has been the case as long as we've had those instruments and those plans, and I don't think there's anything substantially changed since then."
U.S. officials have publicized the new bomb partly to rattle the Iranians. Some Pentagon officials warned not to underestimate U.S. military capabilities even if the bunker-busters can't eliminate Iran's nuclear program.
Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, suggested at the same Pentagon news conference Thursday that airstrikes might be ordered multiple times if Iran tries to build a bomb.
The military option "isn't used once and set aside," he said. "It remains in place. ... We will always have military options, and a massive ordnance penetrator is one of them."

Just as important, the danger from an Iranian response is quantitatively and qualitatively of a different magnitude than Saddam in 1981 or Assad in 2007 could have posed.
That's why leaders of the national security establishments in both Israel and the U.S. have warned about what such operations will entail. Short of a total invasion and occupation of that nation of more than 75 million people, the deployment of Iranian nuclear weapons can only be delayed, not halted, by military action. And the resulting carnage and chaos throughout the Middle East would make the U.S. conflicts in Afghanistan and Iraq seem like picnics in comparison.
At a minimum, thousands of Iranian civilians would die in an American attack against Tehran's nuclear installations. Even if the Israelis alone launch a strike against Iran's nuclear sites, Tehran will almost certainly hit back against U.S. targets in the Straits of Hormuz, in the region, possibly in Europe, and even potentially in the American homeland. And Israel would face certain retaliation from Hezbollah rockets launched from Lebanon and Hamas missiles raining down from Gaza.
That's why it came as no surprise in May 2012 when a majority of Netanyahu's own defense chiefs opposed an Israeli strike on the mullahs' nuclear facilities. That same month, the New York Times reported that Israel's former intelligence chief Meir Dagan "has said that a strike on Iran's nuclear installations would be "a stupid idea," adding that military action might not achieve all of its goals and could lead to a long war." Why?

"A strike could accelerate the procurement of the bomb," claimed Dagan, who spoke at a conference held at the National Security Studies Institute in Tel Aviv. "An attack isn't enough to stop the project."
Dagan posited that military action would align the Iranian population behind the regime, thus solving the country's political and financial problems. Moreover, he asserted that in the case of an Israeli strike, Iran could declare before the world that it was attacked even while adhering to agreements made with the International Atomic Energy Agency - by a country that reportedly possess "strategic capabilities."
"We would provide them with the legitimacy to achieve nuclear capabilities for military purposes," he said.

Short of a large-scale invasion and occupation of Iran by American forces, U.S. military action might still only delay the Iranian bomb Tehran would doubtless go into overdrive to produce. That's why former Bush Defense Secretary Bob Gates and CIA head Michael Hayden raised the alarms about the "disastrous" impact of supposedly surgical strikes against the Ayatollah's nuclear infrastructure. As the New York Times reported in March 2012:

A classified war simulation held this month to assess the repercussions of an Israeli attack on Iran forecasts that the strike would lead to a wider regional war, which could draw in the United States and leave hundreds of Americans dead, according to American officials.

And the costs in lives and treasure would be staggering. In November 2012, the Federation of American Scientists estimated that a U.S. campaign of air strikes would cost the global economy $700 billion; a full-scale invasion could have a total impact of $1.7 trillion. Two months earlier, a bipartisan report signed by ex-National Security Advisor Brent Scowcroft, retired Admiral William Fallon, former Republican Senator and Pentagon chief Chuck Hagel, retired General Anthony Zinni, former Ambassador Thomas Pickering and others warned Americans about the cost of trying to eliminate the Iranian nuclear program once and for all:

A unilateral Israeli attack would set back the Iranian nuclear program by only 2 years and an American attack by 4 years. But if the objective is "ensuring that Iran never acquires a nuclear bomb," the U.S. "would need to conduct a significantly expanded air and sea war over a prolonged period of time, likely several years." In order to achieve regime change, the report says, "the occupation of Iran would require a commitment of resources and personnel greater than what the U.S. has expended over the past 10 years in the Iraq and Afghanistan wars combined."

The anticipated blowback?

Serious costs to U.S. interests would also be felt over the longer term, we believe, with problematic consequences for global and regional stability, including economic stability. A dynamic of escalation, action, and counteraction could produce serious unintended consequences that would significantly increase all of these costs and lead, potentially, to all-out regional war.

After reviewing the results of a 2004 war gaming exercise conducted by The Atlantic in conjunction with leading national security experts, James Fallows last month was moved to ask, "Would a U.S. Strike Against Iran Actually Work?"

Israel doesn't have the military capacity to "stop" Iran from getting a nuclear weapon, and neither does the United States, at least not in circumstances short of total war.

If this all sounds like the hypothetical scenarios of a bunch of doves in the Pentagon and the State Department, it is worth recalling the America reaction to the 1996 bombing of the Khobar Towers in Saudi Arabia which killed 19 U.S. servicemen and wounded hundreds of others. As former Clinton and Bush counter-terrorism chief Richard Clarke recounted in his book, Against All Enemies, President Clinton and the Joint Chiefs contemplated a massive U.S. invasion of Iran in response to the involvement of its agents:

In our meeting with the Pentagon in 1996, Shali was talking about all-out war. The military had a plan for almost any contingency. The plan on the shelf for war with Iran looked like it had been drawn up by Eisenhower. Several groups of Army and Marine divisions would sweep across the country over the course of several months.

Ultimately, President Clinton opted against the invasion of Iran, in part because of the difficulty in proving the U.S. intelligence case against Tehran to the international community. In the end, the U.S. launched a large-scale covert action campaign against Iranian intelligence assets worldwide. Apparently, the message was received with zero distortion; Iran has not targeted United States interests since.
As the P5+1 talks reach what may be their make-or-break moment, there is little disagreement about the risks for regional nuclear proliferation Iran could pose. Saudi Arabia, Egypt and Turkey are just some of the Sunni countries whose initial nuclear efforts could accelerate. But opponents of the deal now taking shape fall into one of two camps. For the likes of Bolton and Muravchik, no combination of sanctions and monitoring will prevent the Islamic Republic of Iran from building nuclear weapons. For Benjamin Netanyahu and his GOP and Democratic allies in Congress, only tougher sanctions and greater pressure will bring "a better deal" to prevent an annihilationist nuclear Iran from wiping nuclear Israel off-the-map with a first strike.
(Of course, there's a glaring contradiction there: the same mullahs in Tehran who are rational enough to cave to public pressure over the pain of sanctions are sufficiently irrational to launch a nuclear exchange in which Iran would be reduced to radioactive rubble by Israel and/or the United States. As Matthew Duss tweeted, "Here we go: Iran is run by crazy suicidal apocalyptic mullahs who will crack under greater economic pressure.")
With the conflicting messages from the Obama administration, Congress and the Netanyahu government in Israel, it's no wonder the American people are confused.

A poll released this week by the Chicago Council on Global Affairs found that 59 percent of Americans supported the deal with Iran currently being pursued by the U.S., UK, France, Germany, China and Russia. At the same time, "nearly six in ten support US airstrikes against Iranian nuclear facilities if Iran violates the deal" and "two thirds support using US troops to stop Iran from obtaining nuclear weapons." But the real costs of either a failure to secure a deal (an unconstrained and unmonitored Iran able to continue nuclear development as the sanctions regime collapses over time) or a preventive war to eradicate Tehran's nuclear capabilities are left undiscussed.
The risk, as a Wilson Center analysis warned, is "a dynamic of action, escalation and counteraction [which] could produce serious unintended consequences that would...lead, potentially, to an all-out regional war." As Dalia Dassa Kaye, director of the Center for Middle East Public Policy at the nonpartisan Rand Corporation put it:

"A military strike would result in the worst of all worlds. It may eliminate some facilities. But it would not eliminate Iranian scientists' technical know-how and would likely further incentivize Iran to pursue a weapon at all costs."

To put it another way, American bunker-busters could produce a bloodbath in the Middle East, Europe and even here at home while busting the U.S. budget as well.