Striking Power. John Yoo

imminence test placed its emphasis on timing because of the nature of early nineteenth-century weaponry. Fleets and armies moved slowly, their weapons engaged at short range, and they relied on primitive munitions. An enemy nation could not inflict crippling losses in a surprise attack. Nations could afford to wait until an attack became more certain because the risk of destruction was not great. A large-scale invasion would reveal itself because of the preparations involved. Even by the time of World War I, the European great powers required several weeks to mobilize their massive armies, as Barbara Tuchman vividly described in The Guns of August.²² The Caroline test seems much less compelling when the threat comes from a hostile state intent on acquiring WMD and the means to deliver them quickly. To wait for peaceful resolution may mean waiting until the target state has already passed the nuclear threshold. It would be vastly more dangerous to take preemptive action against a state that has already acquired nuclear weapons.

      In the face of such change, self-defense must expand beyond temporal imminence. Technological advance has increased the destructiveness of modern weapons, while making them harder to detect, quicker to launch, and cheaper to build. Nations should have the ability to use force even earlier than in the Caroline test, which involved a dispute between two friendly nations with armies and navies propelled by horses and sail and armed with cannons and muskets. Even if the probability of an attack has declined, the increase in magnitude must mean that nations can use force earlier to forestall it.

      The Cuban Missile Crisis demonstrates the workings of such an approach. Moscow’s secret deployment of medium-range nuclear missiles only ninety miles from the U.S. posed a threat to American national security and would have upended the balance of power. While the Soviets were transporting missile components by ship, it appeared that they had neither fully assembled nor fueled the weapons. No attack was imminent in a temporal sense. Nonetheless, President John F. Kennedy ordered a naval “quarantine” on Soviet shipments to Cuba—a use of force that blocked navigation around Cuba and threatened the boarding and detention of Russian ships and crew. He argued that Nikita Khrushchev’s dispatch of the missiles “add[ed] to an already clear and present danger” because “we no longer live in a world where only the actual firing of weapons represents a sufficient challenge to a nation’s security to constitute maximum peril.” He emphasized that the speed and harm of modern weaponry justified earlier action. “Nuclear weapons are so destructive and ballistic missiles are so swift, that any substantially increased possibility of their use . . . may well be regarded as a definite threat to peace.”²³ While scholars at the time debated whether the quarantine violated the Caroline test,²⁴ Kennedy’s measured use of force brought the crisis to an end and was JFK’s finest moment in office.

      The Cuban Missile Crisis also illustrates the promise of more precise uses of force that new weapons make possible. Khrushchev’s deployment brought parts of the U.S. within fast striking range of Soviet nuclear missiles for the first time. The United States did not wait until an attack was imminent to destroy the missiles and launch sites, which could have produced an escalation that led to a broader war. Instead, the United States imposed a blockade that used force in a narrower, less destructive manner, but still rendered it difficult for the Soviets to complete and launch the missiles. The potential harm from a Soviet attack was lower at this earlier point in time, because even though the potential magnitude of destruction from a nuclear attack was still great, there was a much lower probability of it. That expected harm was still high enough—it might even be tantamount to an imminent threat of a less destructive conventional attack—to justify a resort to force. In order to act earlier, however, the United States employed less violent methods than that justified by an imminent attack. Because the expected harm of an attack was lower (due to its greater uncertainty), Kennedy appropriately used more precise, less harmful means to coerce the Soviet Union to withdraw its missiles.

      Preemption looks different when the threat is not so much an immediate attack as a sudden, menacing advance in enemy capacity. That was the threat from Iraq’s nuclear program in the early 1980s. Israel launched an air attack on the Osirak nuclear reactor in 1981 because it believed that Baghdad was creating the components for nuclear weapons. An Iraqi nuclear attack on Israel would have catastrophic consequences, but no such attack could occur until some years into the future. Iraq had not recently attacked Israel, though it maintained its opposition to Israel’s existence.²⁵ Israel acted before the reactor became operational to take advantage of a window of opportunity that would soon close. A later attack could have released radioactive fallout over Baghdad. The U.N. Security Council condemned the attack as a “clear violation of the Charter of the United Nations and the norms of international conduct.”²⁶ Even the United States, which had traditionally protected Israel with its Security Council veto, voted against Jerusalem and condemned the attack.

      At the time, Iraq appeared to be complying with its international obligations for its civilian nuclear program, had not attacked Israel or Kuwait, and seemed preoccupied with its ongoing war against next-door Iran. Still, Israel had the better of the argument. Its ambassador to the U.N. responded that to “assert the applicability of the Caroline principles to a State confronted with the threat of nuclear destruction would be an emasculation of that State’s inherent and natural right of self-defense.”²⁷ Despite his assurances to the contrary, Saddam Hussein continued to pursue WMD and was on his way to a nuclear weapon by the time of the 1991 Persian Gulf War. He had a hostile intent not just against Israel, but Iran to the east and Kuwait to the south. If Saddam had developed nuclear weapons by the time of the 1991 war, U.S. forces would not have succeeded so easily in dislodging Iraqi forces from Kuwait.

      New weapons can make such interventions safer or more feasible to pursue. Beginning in the late 1990s, the United States protested efforts by Iran to secure a reserve of weapons-grade uranium fuel that could be used for nuclear weapons. Successive administrations seem to have cautioned Israel not to launch its own air attack on Iranian nuclear facilities, lest this provoke a dangerous level of conflict in the Middle East at a time when Iran was already supporting Shia militia in Lebanon and, after 2003, in Iraq.²⁸ Instead, the United States launched an elaborate cyber attack on the Iranian nuclear program. Stuxnet may have set back the Iranian program for a few years without causing any direct injury to human beings. It is not certain that bombardment from the air could have done better, and it more likely would have caused more casualties. Iran no doubt would claim many of the deaths were civilian, since it has always insisted that its nuclear program was for peaceful purposes. Nevertheless, Stuxnet might have created the conditions for more favorable terms in subsequent negotiations. In its eagerness for a deal, however, the Obama administration seemed to have forfeited the leverage provided by the cyber attack.

      The cyber attack might have worked longer-lasting harm to Iran’s uranium processing equipment. The Iranians could see that centrifuges were malfunctioning and had to be replaced, but they did not learn the cause for some time.²⁹ The United States government did not acknowledge its role in developing or infiltrating the computer codes that caused the damage. Ambiguity about the source of the attacks may have made the intervention less provocative and confrontational compared with an air strike. The uncertainties made it easier for both sides to avoid immediate charges and countercharges and an escalation of hostilities. Officials in the Bush and Obama administrations understood that a stealthy cyber attack on the Iranian program would be less threatening to the Iranian regime.³⁰

      Critics will claim that these new weapons will make unilateral intervention too attractive. Their very ease, precision, and light impact will encourage nations to resort to force in lesser or more highly focused increments. Bombing a city or landing thousands of troops will challenge a nation’s sovereignty and spark demands for a military response. But a highly focused attack with specialized technology, which does little direct injury to civilian life, may give nations the flexibility to respond with diplomatic protests and a peaceful resolution.

      It may be that new technologies will encourage an overly complacent attitude toward preemptive or preventive attacks. Still, we must balance this risk against the risks involved when states remain passive while WMD fall into reckless or threatening hands. Western nations may best counter the ambitions of an Iran or North Korea with high-tech weapons, which might force rogue states to the negotiating