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 — or any government — in foreign conflict should be treated with great skepticism.

Second, war creates big government. That’s one reason libertarians and other believers in limited government have tried to avoid war. Throughout history, war has provided an excuse for governments to arrogate money and power to themselves and to regiment society.

During World Wars I and II, the United States government assumed powers it could never have acquired in peacetime — powers such as the military draft, wage-and-price controls, rationing, close control of labor and production and astronomical tax rates. Constitutional restrictions on federal power were swiftly eroded.

That doesn’t tell us whether those wars should have been fought. It does mean that we should understand the consequences of war for our entire social order and thus go to war only when absolutely necessary.

Third, the United States can no more police and plan the whole world than it can plan a national economy. Without a superpower threat to rally against, the political establishment wants us to deploy our military resources on behalf of democracy and self-determination around the world and against such vague or decentralized threats as terrorism, drugs and environmental destruction. The military is designed to fight wars in defense of American liberty and sovereignty; even the world’s largest bureaucracy is not well-equipped to be policeman and social worker to the world.

Fourth, our Cold War allies have recovered from the destruction of World War II and are fully capable of defending themselves. The countries of the European Union have a collective population of more than 500 million, a gross domestic product of $18 trillion a year and nearly 2 million troops. They can defend Europe and deal with internal problems such as the conflict in Ukraine without U.S. assistance. South Korea has twice the population and 40 times the economic output of North Korea; it doesn’t need our 29,000 troops to protect itself.

Fifth, the communications explosion means that the information imbalance between political leaders and citizens is much reduced. For all our vast intelligence network, presidents often watch world events unfolding on satellite news networks, along with all the rest of us. That means that presidents will find it more difficult to expect public deference on matters of foreign policy, so they should proceed cautiously in undertaking foreign commitments without popular support.

Despite the constant warnings of war hawks, and the ongoing images of conflict on our screens, the world is safer than it’s ever been. And for the United States, the most secure power in world history, protected by two oceans and friendly neighbors, that’s especially true.

The first purpose of government is to protect the rights of citizens. We must maintain an adequate national defense, but we can defend the vital interests of the United States with a military budget about half the size of the one we have — if we reorient our foreign policy to one of self-defense and restraint, not global commitments to collective security agreements.

Libertarians who propose to bring U.S. troops home and concentrate on the defense of the United States are sometimes accused of being isolationist. That’s a misconception. Libertarians are, in fact, confident and cosmopolitan. We look forward to a world bound together by free trade, global communications and cultural exchange. We support maintaining the world’s largest and most powerful military, by a wide margin, although not as big as the foreign-policy establishment wants.

Military intervention around the world costs Americans substantial blood and treasure and benefits them little. Although the world is growing closer together in many ways, it is inappropriate to view the whole world as a village in which everyone must pitch in to stop every fight. In a world with terrorism and nuclear weapons, it is better to keep military conflicts limited and regional rather than to escalate them through superpower involvement.