Five Rules for an Age of Terrorism, Nuclear Weapons

In this 15th year of war in Afghanistan, as the United States is becoming further entangled in military conflicts in Iraq, Syria and Yemen, we need a serious debate about whether we want to be permanently at war.

We can start by noting a few simple rules about war and foreign policy. First, war kills people. Especially in the modern world, it often kills as many civilians as soldiers. War cannot be avoided at all costs, but it should be avoided wherever possible. Proposals to involve the United States —...