 Welcome to the Naval War College, the Navy's home of thought. We are excited to present a new series titled NWC Talks, where we showcase our world-class experts in discussing national security matters. We hope you enjoy the conversation. During the Cuban Missile Crisis in 1962, President John F. Kennedy warned the nation that we no longer live in a time when the actual firing of weapons constitutes maximum peril to the nation. What did he mean? Why have we changed the way we think about going to war? Traditionally, we've gone to war for self-defense. In the 21st century, has that changed? I'm Professor Tom Nichols of the National Security Affairs Department at the Naval War College, and this is NWC Talks. Traditionally, states have gone to war for self-defense, for conquest, for honor. But in the modern era, we have two primary kinds of war, preemptive and preventive. This is an important distinction because we're changing these definitions in the late 20th century and into the 21st century. Now going to war for self-defense is always acceptable. If someone attacks you, you're attacked at Pearl Harbor, for example. You can respond and fight back against the aggressor. But what if someone's only about to attack you? What if you suddenly realize that you are in imminent peril? This leads to the problem of preemptive war, of striking ahead of the enemy's attack. But what if you face an enemy who isn't yet ready to attack you and down the line might attack you? Can you strike simply because you're ready and your opponent is not? That's the problem of preventive war. Traditionally, preemptive war is acceptable, preventive war is not. And we need to talk about the difference between those two kinds of conflict. Preemptive war in its simplest form is kind of like the bar fight where someone's about to hit you, you realize you're about to be hit, and you hit them first. What if a cop in the world arrests you for that? You're in a case of anticipatory self-defense. The textbook example of this, and literally the example you will find in textbooks, is the Six-Day War in 1967 between Israel and her Arab neighbors. Very clear warning of an attack, massing of forces, announcements and propaganda indicating an attack would be soon to take place. The Israelis struck first, spoiled the attack, and that really is the definition of a preemptive war. It's a spoiling attack. In some ways, the 1967 war was too perfect. Most enemies don't give you that much warning that they're about to attack. But in tradition, an enemy, massing forces, about to attack you, you are well within your rights to strike first. That's different from preventive war. Preventive war is when you decide that there is a threat brewing and that at some point this threat could become a mortal peril. This is like President Kennedy talking about a threat in advance of the actual firing of weapons. And this is very important because traditionally, preventive war, for those of you who have brothers and sisters, this is like hitting your little brother for the thing he's about to do. In a more serious vein, preventive war is striking at an enemy who might be an enemy, who might create a war down the line. This is like the scene in Godfather 2, if anyone has ever seen the sequel to the Godfather movies, where a mafia don decides to kill a young child because he's afraid that the child will come back and seek revenge on him. That is preventive war thinking. This plays out in international relations in several cases in history. Athens and Sparta, the two Greek city-states of the 5th century B.C., where Athens decides that it may need to go to war with Sparta, but Sparta wants that war because, as the Spartan Council says at the time, because of the rising power of Athens. They want a war that's going to snuff out what they believe is a future Athenian threat. The Japanese attack on Pearl Harbor, classic preventive war. The Japanese decide that their goals require the elimination of the United States Navy. They decide to attack at Pearl Harbor and simply end that duel before it even begins. The German invasion of Norway out of fear that the British may occupy Norway, a classic case of preventive war. When I say that this is unacceptable in the case of Norway, there are people who went to Nuremberg and were put on trial for their lives for violating this precept against preventive war because if you think about it, preventive war is perpetual war. Once you decide that you can stomp out threats rather than actual imminent peril, you pretty much have decided that you can go to war at will. Now, this is a problem for us here in the United States in particular in the 21st century since we have made the case over the past many years, including in the Second Iraq War, that we may need to go to war to snuff out threats that are years down the line. And you'll see that the United States is not alone in this. If you look through the past 10 or 15 years of statements from countries like France, Australia, Russia, even Japan, there is an increasing unwillingness, especially after 9-11, there is an unwillingness among major nations to wait to be attacked, in part because it's now difficult to know when you're about to be attacked. The days of massing forces are long gone. Today, a threat can brew hidden inside a mountain, underneath in a bunker, in a laboratory, and major states are no longer willing to wait to see if those threats are going to coalesce into imminent peril. Now, there is actually a rule in international relations that governs this. It's called the Caroline test, named for a ship called the SS Caroline that was running guns to rebels in Canada. I know rebels in Canada sounds odd, but remember this was part of the British Empire and there were always rebels in it. And the Americans were running guns through Niagara Falls on a ship called the Caroline. And the British commander had had enough of this and he lit the Caroline on fire and threw it over the falls. Unfortunately, it also had a few Americans in it when he did that. This led to a diplomatic incident between the United States and Great Britain in the 1830s and 1840s that took some years to straighten out, but it resulted in a formulation that the United States and Great Britain agreed on on the use of force, that the threat had to be instant, overwhelming, leaving no time for deliberation and no other means. And for years, this entered the literature of international law as the Caroline test, that if you used force as a state, did you face a threat that was instant and overwhelming and you had no other choice? That's why Pearl Harbor fails that test, the invasion of Norway fails that test. A lot of legal scholars would argue that the invasion of Iraq failed that test. And yet, countries are increasingly willing to engage in thinking about that kind of activity and to reach out in part because they're no longer dealing with other nation states, they're dealing with non-state actors and terrorists. And so now we have a world in which preventive war, which the great Prussian statesman Bismarck once referred to as committing suicide out of a fear of death, preventive war is now entering the lexicon as almost as legitimate as preemptive war. And that's because states don't feel they have enough warning of an imminent attack anymore. If you think about how preemptive, the legitimacy of a preemptive strike would have worked and you go back to the 20th century. If the United States had seen the Japanese fleet on the night of December 6th or if the Soviet Union had seen the massing Nazi armies, which they did, they just didn't believe what they were seeing, if they had decided to attack the massing Nazi armies or if the United States had decided to get the jump on the advancing Japanese fleet, that would have been perfectly legitimate. That would have gone into the history books as a spoiling attack as well. But if you're a leader now in the 21st century, what do you do about the fact that your opponents, who may not be states, are not going to mass a million-and-a-half crack combat troops on your border or that they are not going to show up steaming across the Pacific with carriers and bombers and torpedoes? If your opponent isn't that kind of enemy and doesn't give that kind of warning, when are you justified in breaking what is a normal prohibition on the use of force? Remember, all United Nations members are constrained in their use of force. They are limited to self-defense or to, in rare cases, the execution of the will of the Security Council. So what do you do when your opponent isn't a state, doesn't mass forces, is in hiding? And the threat has a long fuse that could take years before it actually culminates to go back to President Kennedy's comments as the actual firing of weapons. One new wrinkle here is that states are sometimes cloaking preventive action under the rubric of humanitarian intervention. This is a tragedy because humanitarian intervention is a real thing. Sometimes it needs to be done. There are places in the world where innocent lives are in danger and they need to be protected. On the other hand, as we've seen in places like Ukraine, where the Russians have argued that they need to intervene to protect the rights of their Russian-speaking brethren, and in other parts of the world, even now the United States talking about an intervention in Venezuela, you can see where large states want to intervene proactively. One might say preventively to snuff out what they think are either threats to their security or to threats to their foreign policies. And this is part of the danger of preventive war. It becomes a slippery slope where if you decide that you're going to snuff out a future WMD threat, then it's a short jump from there to saying you can take military action simply to keep the world adjusted to your foreign policy priorities. In my view, this is an unbelievably dangerous development, but it's also a perfectly understandable one in a world where terrorists, rogue states, the proliferation of weapons of mass destruction technology have made complications and created complications for decision makers that make the old dilemmas of the Cold War seem simple and binary by comparison. I'm Tom Nichols. This has been NWC Talks.