Almost no one opposed retaliatory air strikes on the grounds that intervention, in itself, would run contrary to international norms. The Chemical Weapons Convention prohibits the production, stockpiling, and use of chemical weapons, such as sarin and VX nerve gas.7 But it does not authorize the use of force against violators; it only empowers states to refer a situation to the U.N. Security Council. In any case, Syria never signed the CWC. The U.N. Charter empowers the Security Council to authorize the use of force to protect against threats to international peace and security, for which the Syrian civil war or the use of chemical weapons might qualify. Despite pressure from the United States, Britain, and France, however, the Security Council could not act because of the vetoes of Russia and China.8
It was hard to see the Obama administration’s proposal as anything other than “punishment.” The White House denied that intervention would aim at influencing the outcome of the civil war.9 The announced goal was to “impose a price” for using such terrible weapons, or, in more direct terms, to “punish” the Assad regime. The administration did not propose air strikes to destroy the chemical weapons stockpiles or their production facilities. The aim was simply to impose some “cost” elsewhere to deter future use of the weapons. Critics warned that the tactic would prove ineffective or have unacceptable side effects, but not that it was, in itself, improper.10 The Obama administration finally embraced an alternate policy, an agreement with the Syrian and Russian governments for the internationally supervised removal of the chemical weapons.11 Administration spokesmen insisted, however, that this outcome had only been possible because it had previously threatened Syria with punitive strikes.12
The Obama administration’s approach to Syria predictably failed. Syria continued its brutal civil war that has killed an estimated 470,000 people, most of them civilians.13 The Assad regime continues to use chemical weapons, though perhaps not in the amounts that it would have without the agreement. The remaining Syrian population that could flee has left the country. According to some estimates, more than four million Syrians have become refugees, destabilizing the region and pressuring even NATO allies.14 In the power vacuum left by withdrawing U.S. forces in Iraq, al-Qaeda transformed into ISIS and seized large swaths of territory in both countries. ISIS has imposed a draconian version of Sharia law on the people under its control and created a safe haven where it can train new fighters from around the world. Along with the United States, Turkey has declared that the Assad regime must go and has crossed the border in force to root out ISIS. Meanwhile, Russia and Iran have sent unconventional fighters, regular troops, and modern air power to prop up the Assad regime.
The Syrian civil war illustrates the threats to peace in the twenty-first century, which now come less from great power war and more from rogue nations, terrorist groups, and failing states. Though the threat of general war has receded, these new challenges may demand that states use force more often, but at lower levels of intensity. Civil wars and humanitarian crises, however, may deter intervention because of the possibility of high casualties in urban environments. Terrorists and guerrillas refuse to follow the laws of war by refusing to distinguish themselves from civilians, hiding among them, and launching terror attacks on them. WMD and rogue nations present further difficulties because of the covert nature of their weapons programs and their disregard for the lives of their own civilians. Left to fester, these challenges can grow into serious threats to international stability, whether from terrorist attacks, the deaths of thousands of civilians, or authoritarian regimes armed with nuclear weapons. New technologies can help the great powers address these threats by applying force with greater precision at less cost.
Preemption and WMD Threats
Weapons of mass destruction pose new challenges. Widespread destruction has always been a possibility in war. In ancient times, the civilized states of Greece and Rome sometimes massacred or deported all the inhabitants of an enemy city. But before the twentieth century, the possibility for casualties had not reached millions from a single strike. A hostile army also had to invade enemy territory before it could slay and destroy. Now nuclear weapons can wreak devastation in the first minutes of conflict and, if widely used, destroy most human life on earth. Even the detonation of a single nuclear weapon in the United States could kill vast numbers of people and severely disrupt our society. Nations have an interest in keeping these most destructive weapons out of the hands of the most reckless leaders, especially those who might use them impulsively or share them with terrorists.
It is not unusual for a sudden change in arms to generate a strategic threat. In such circumstances, western leaders once thought that they could act preemptively before such a threat had matured, even before an attack was “imminent.” In 1807, for example, Great Britain feared that Denmark and Norway would transfer their fleets to France, which would have allowed France to challenge the Royal Navy’s control of the seas. Instead, after the Danes refused to hand their fleet over to the British, a British fleet bombarded Copenhagen for three days. The Danes changed their minds and gave up their fleet. The British government defended this intervention against a neutral nation as an act of “self-defence.”15 Great Britain took similar action in July 1940, after France had signed an armistice with Germany. Churchill ordered an attack on the French fleet in North Africa to prevent its transfer to German control. Most observers did not condemn this vivid demonstration of Britain’s determination to go on fighting.16
But modern weapons have multiplied the destructiveness of attacks while accelerating their speed and surprise. To be sure, it may still take weeks, or months, to put a conventional armed attack in motion. The United States required months to assemble the invasion forces in the Persian Gulf War of 1990 and the Iraq war of 2003. But stealth bombers, hypersonic cruise missiles, and ballistic missiles have reduced the time for an attack to be detected, not to mention stopped. A ballistic missile can drop a nuclear warhead on a city in thirty minutes.17 Ballistic missile technology has even spread beyond the arsenals of the great powers to rogue nations like Iran and North Korea.
Nuclear weapons threaten a magnitude of destruction that goes well beyond the transfer of a fleet in the nineteenth or twentieth centuries. They could cause devastating and indiscriminate long-term damage to the civilian population and the environment. A single five-megaton nuclear blast, for example, would generate a 2.8-mile-wide fireball, heat of 14,000 degrees Fahrenheit (the sun is 11,000 degrees F), winds ten times stronger than a hurricane, a ground shock 250 times worse than any earthquake, and air overpressure of 500 pounds per square inch.18 In 1996, the International Court of Justice observed that such weapons possess unique characteristics, “in particular their destructive capacity, their capacity to cause untold human suffering, and their ability to cause damage to generations to come.”19 The spread of ballistic missile technology and advances in miniaturization have allowed even Third World nations to develop the capacity to launch nuclear attacks with little warning. The magnitude of harm threatened by WMD has grown, their detection has become more difficult, and the time necessary for their launch has dropped.
The calculus of war must shift to meet these technological developments. In order to prevent the possible use of WMD, nations should resort to force earlier depending on the nature of the threat. As many scholars and international tribunals have read the U.N. Charter, nations are now prohibited from using force except in two situations: in response to “an armed attack” or by authorization of the U.N. Security Council. On the other hand, most scholars acknowledge that nations may launch attacks to preempt an imminent attack before an enemy has crossed the border.20 In the famous case of the Caroline, in which British forces pursued Canadian rebels across the U.S. border, Daniel Webster argued a nation could use force in anticipation of an attack that is “instant, overwhelming, leaving no choice of means, and no moment for deliberation.”21 The Caroline test, which the Nuremburg tribunal and the ICJ Nicaragua decision attempted to elevate to the status of universal customary law, appears to create a high bar for the use of force. But it also contains the seeds of a broader understanding of war more appropriate