Even as they condemn terrorism, nation states have embraced it. Attacking civilians is not a defining feature of terrorism: every war sees civilians targeted. The real criterion of terrorism is the attacker’s limited liability. The idea of terrorism is to hit and run. Normally, terrorists hide among civilians, but they can also find escape in mountains as the ancient Assassins did, or into jungles like the Vietnamese communists. But there is an often-overlooked option for limiting the attacker’s liability: if he is much stronger than his victim, the victim won’t dare to attack lest the fighting escalate. In that sense, the American wars in Korea, Vietnam, Afghanistan, and Iraq are pure terrorism. That does not imply any moral judgment: I deeply respect Muslim terrorists and sided with the Americans in their Vietnamese debacle, though not in the senseless wars in Afghanistan and Iraq.

WWII was the last war between civilized countries; since then, they only embark on terrorist missions because their voters won’t support a campaign in which they would be targeted. That, incidentally, supports the argument that Vietnamese communists would have been justified in attacking the American mainland. Whether such action would have been feasible is another matter: the American people might have reacted like they did after Pearl Harbor or 9/11, and supported stronger action overseas. Repeated attacks against the mainland might have shored up the isolationists and prompted the Americans to withdraw from Vietnam sooner.

In recent years civilized states have engaged in explicit terrorism as well. Unwilling to attack their enemies with conventional means, they resort to covert operations. They do not target civilians, but many terrorists view civilian casualties as collateral damage, too: in Yemen, Al Qaeda attacked a US battleship, and in Africa, they attacked American embassies; not exactly neutral civilian institutions. In Iraq during Saddam’s rule and in Iran Western intelligence agencies conducted a war which took hundreds of enemy lives. Politically unable to invade Syria or Lebanon, Israel operates there through the Mossad and Aman agencies.

States’ interest in terrorism stems from their unwillingness to make wars. There are three reasons for that unwillingness. First, war is no longer a respectable continuation of diplomacy by other means, but a brutish, politically incorrect affair. Democratic rulers can ill afford to have their voters come home in coffins. “Human rights” liberals and commonsense citizens have found common ground in their opposition to dangerous wars.

Second, wars became prohibitively expensive. In today’s dollars, WWII cost America about $3.5 trillion. Two meaningless operations in Iraq and Afghanistan cost a third of that. The necessity of using humane methods drove up the cost of killing, and the best medicine turned conscripts from free to very expensive. The cost of armaments, always at the cutting edge of technology, grows faster than average goods, thus weapons become relatively more expensive and wars consume a higher percentage of GDP.

Third, WMD have made wars very dangerous. For the USSR and Germany, WWII was no less destructive than a nuclear exchange, but nuclear war is fast and unforgiving. Generals have always complained that new weapons are so destructive that they take the art out of war, but only nuclear weapons made that maxim certain. In the age of actual use of nuclear weapons, there will be no battles: mobility and maneuvers mean nothing when mega-bombs simply obliterate the armies and create impassable radiation zones.

Terrorism is not a modern aberration, but a return to the historical norm when states lacked a monopoly on violence. And weak states cannot be big.