According to New Yorker columnist Seymour Hersh, the Bush administration is contemplating "the use of a bunker-buster tactical nuclear weapon, such as the B61-11, against [Iran’s] underground nuclear sites." Presumably, the B61-11 nuclear bomb can be configured with yields low enough to be categorized as a mini-nuke, i.e., sub- or only a few kilotons. Currently considered a "dumb bomb," theoretically, the B61-11 could be mated with GPS guidance to achieve the same precision as the Joint Direct Attack Munition (JDAM), which where used to great effect
in Afghanistan and Iraq. Also, the B61-11 could theoretically be outfitted with the the BLU-113 hardened steel-tipped warhead to penetrate more than 30 feet of concrete and a delayed-action fuse to penetrate the structure before exploding, thereby concentrating the destructive force on the inside of the target instead of on the surface. Therefore, on paper, the United States has a low-yield nuclear bunker-busting capability more commonly referred to as a mini-nuke.
Advocates of these mini-nukes argue that they are needed because adversaries are building underground facilities to conceal and protect their weapons of mass destruction (WMD) programs, such as Iran’s nuclear program. They also contend that because mini-nukes have a relatively small yield, they are less destructive and therefore more usable that is, they would be relatively benign compared to using a nuclear weapon detonated above ground and would inflict less collateral damage.
It is worth noting, however, that nuclear tests conducted in the 1960s (named "Plowshare") using relatively low-yield weapons buried 30 meters or deeper underground resulted in craters the diameter of a football field, with 10 to 50 percent of the mass of the crater resulting in local radioactive fallout extending as far as several kilometers. According to Princeton University physicist Robert W. Nelson, a "one kiloton earth-penetrating ‘mini-nuke’ used in a typical third-world urban environment would spread a lethal dose of radioactive fallout over several square kilometers, resulting in tens of thousands civilian casualties." So a mini-nuke might cause considerably less damage than a "conventional" nuclear weapon, but the damage would still likely be very considerable.
Any consideration of using mini-nukes against Iran should be tempered by the experience of the Iraq war the first test case of the Bush administration’s policy of preemption. Iraq highlights the problem of combining mini-nukes and preemption: the Bush administration’s threshold for preemption and thus for the possible use of nuclear weapons is at best, ambiguous, and at worst, dangerously low. By the standards set forth in the latest incarnation of the National Security Strategy of the United States "to forestall or prevent such hostile acts by our adversaries, the United States will, if necessary, act preemptively in exercising our inherent right of self-defense" the simple existence of conditions where one of many possible outcomes might be the emergence of a threat is sufficient to preempt. Thus, the litmus test is the plausible allegation of a potential threat but not the convincing proof of the existence of such a threat. Speculation about unknown future intentions and capabilities of potential enemies becomes a casus belli.
Prior to going to war, the administration alleged that Iraq had weapons of mass destruction, including the possibility of being on the verge of acquiring a nuclear weapon. More ominously, the administration claimed that Saddam Hussein could give WMD to al-Qaeda terrorists. But more than three years after invading Iraq, no WMD have been found. Moreover, the CIA has found no evidence that Hussein tried to transfer WMD to terrorists, al-Qaeda or otherwise. In other words, all the hoopla about Iraqi WMD amounted to at best next to nothing.
Thus, the reality of Iraq compared to the prewar rhetoric hardly creates confidence that mini-nukes would only be used when circumstances warrant. In fact, the Iraq war suggests just the opposite. If the administration had had mini-nukes, it might have used them in a preemptive fashion on the slim pretext of alleged WMD (which didn’t exist), which supposedly would have been given to al-Qaeda terrorists, who weren’t in league with the former regime in Baghdad.
The inability to find any WMD to date highlights another problem with the possible use of precision mini-nukes to destroy WMD facilities: very precise delivery of weapons to the wrong place. Before and during the Iraq war, administration officials implied that they were relatively certain where WMD were located, including aerial photographs shown by Secretary of State Colin Powell at the United Nations Security Council when he made the administration’s case for military action in February. But suspected WMD locations have turned up empty. So even if Iraq had WMD (if you are willing to believe Hussein was so good at hiding them that they still can’t be found after three years of searching), had the United States used mini-nukes, it might have used nuclear weapons against the wrong targets, i.e., facilities that did not contain any WMD.
Moreover, unlike in June 1981, when Israel conducted a successful preemptive attack against Iraq’s Osirak nuclear reactor, Iran’s nuclear program consists of tens if not hundreds of potential targets. And many of those targets are co-located in highly populated areas. So even the most precise strikes are likely to result in large numbers of civilian casualties.
The Iraq war also calls into the question the usability of mini-nukes. On at least two occasions, U.S. intelligence indicated that Saddam Hussein was thought to be in underground bunkers that were subsequently attacked with conventional weapons. If Hussein was arguably the highest value target in Iraq during the war, then a good case could have been made for using a nuclear weapon like the B61-11 to assure killing him and decapitating the regime, which was part of the overall U.S. war strategy. But the fact that the United States chose not to use the B61-11 during the Iraq war suggests that either (a) even a relatively low-yield nuclear weapon detonated underground would produce too much damage, particularly if located in a densely populated urban area such as Baghdad or (b) there is a real stigma or aversion to U.S. first use of nuclear weapons, even against adversaries who cannot retaliate in kind.
What is troubling if Seymour Hersh is to be believed is that the White House is unwilling to take the preemptive nuclear strike option against Iran off the table, which implies that both (a) and (b) above may not hold. As Hersh points out, many senior officials in the Bush administration including National Security Adviser Stephen Hadley and Undersecretary of Defense for Intelligence Stephen Cambone have previously advocated using nuclear weapons against high-value targets. But in the final analysis, mini-nukes and preemption are a dangerous combination that could undermine deterrence and make the United States less secure. If rogue-state leaders believe that the United States has targeted them for regime change regardless of any actions they might take short of abdicating power to a new leader deemed acceptable by the United States and is willing to use nuclear weapons preemptively, they may feel they have nothing to lose by using what they can, including WMD, to strike at the United States first.
Furthermore, if rogue-state leaders do not possess the long-range military capability to directly attack the United States, and if preemptive regime change is thought to be inevitable, the natural barriers for those leaders to form alliances with terrorist organizations will be eroded, and the incentive for them to see terrorism and possibly supplying terrorists with WMD as the only way to retaliate against the United States will increase.
To be sure, a nuclear-armed Iran would be an unwelcome development. But unless the so-called "mad mullahs" in Tehran are suicidal, there is every reason to believe that the overwhelmingly superior (both in numbers and technology) U.S. strategic nuclear arsenal will act as a powerful deterrent. And even though the Iranian regime has ties to terrorist organizations, there is no evidence that rogue regimes would provide WMD including nuclear weapons to terrorists. Finally, using nuclear weapons against Iran would confirm that the United States is engaged in a war to destroy Islam and likely unleash even more unwelcome developments.