RUTHFULLY YOURS

Nations in decline—democratic ones, at any rate—tend to be nations in retreat. When Britain informed the Truman administration that it could no longer prop up the governments of Greece and Turkey in the winter of 1947, it had already spent a quarter of its national treasure waging World War II and fought beyond the limit of its endurance. As a country it had a future. As a world power it was through.

Question: Is the inverse true? Is a nation in retreat also in decline?

A couple of weeks ago I scored Barack Obama for having no real foreign policy to speak of. But then the president gave a speech last Thursday at the National Defense University that set my complaint to rights. There is, after all, a method, a purpose, a governing idea.

It’s called the Retreat Doctrine.

Or, to put the best gloss on it, it’s the idea that retreat, far from being a symptom or harbinger of decline, is the quickest route to national renewal, economic and moral. “We must define the nature and scope of this struggle,” Mr. Obama said Thursday, “or else it will define us, mindful of James Madison’s warning that ‘No nation could preserve its freedom in the midst of continual warfare.’ ”

That’s a thought that deserves scrutiny, especially because it resonates on both sides of the political aisle. According to the left, the war on terror has meant degraded civil liberties at home, the destruction of America’s good name abroad, thousands of unnecessary deaths in misbegotten wars, “imperial overstretch,” and the diversion of scarce resources from worthy government programs.

As for the right, much of it has quietly conceded that the wars in Iraq and Afghanistan weren’t worth the candle; that the Middle East is a chronic disease to be managed rather than a political problem to be solved; and that a $16.7 trillion debt is a greater threat to national security than some troublemakers in Quetta or Timbuktu.

And so the Retreat Doctrine takes hold. It’s alluring to think that, merely by declaring an end to “continual warfare,” we can end continual warfare; that we can define our problems as we’d like them to be, rather than take them as they are and have them define us in turn.

Thus the operating assumption of Mr. Obama’s speech, and for that matter his entire presidency: Saying it makes it so. Take terrorism: According to Mr. Obama, its future lies in “localized threats” like the attack in Benghazi that didn’t really disturb the peace at home and could be dealt with “smartly and proportionately.” That means that America can finally turn a page on the war on terror, in part by sharply restricting the legal authorities under which it has been conducted.

It’s nice to know we have a president who thinks he’s clairvoyant. And maybe Mr. Obama is right. But nobody knows. What we do know is that the U.S. federal government has just two modes: under-reaction and overreaction. When the default was set to under-react, we got 9/11. We’ve been over-reacting ever since—and have been spared comparable attacks.

A prudent president might stay the course, to borrow a phrase. The Retreat Doctrine counsels otherwise. “What history advises,” Mr. Obama said Thursday, is that “this war, like all wars, must end.” That’s true to the point of truism, though as far as I know Dwight Eisenhower didn’t declare an end to the Cold War in 1958. What history really advises is that America does best when it fights its wars to a successful conclusion. The alternative is to confirm what our enemies suspected all along: We don’t have the stomach for the long haul; all they have to do is wait us out.

But what about all the damage the war on terrorism does to other U.S. interests? Mr. Obama denounced his predecessor for having “compromised our basic values.” Yet nothing President Bush ever did compared with FDR’s internment of Japanese-Americans, or Lincoln’s suspension of the writ of habeas corpus. Historically speaking, the war on terror has been a model of legal and ethical caution.

Mr. Obama also noted that the war had cost the U.S. “well over a trillion dollars . . . exploding our deficits and constraining our ability to nation-build at home.” That sounds like a lot of money, until you consider that federal government outlays since 2002 come to $31.3 trillion and counting. The depressing truth about the war on terror isn’t that it has bankrupted us. It’s that we fought it on the cheap while gorging on entitlements, ethanol subsidies, bridges to nowhere and ObamaCare.

These realities don’t sit well with the Retreat Doctrine—but then, the ultimate purpose of the Doctrine isn’t to revitalize America. It’s to reduce America, as Britain was reduced after 1947, from world-spanning empire to wan social democracy. At least the British had the excuse of the Somme and the Blitz.

To retreat isn’t to decline. But retreat can lead to decline, when a nation develops a taste for it, and when adversaries take advantage of it, and when disasters result from it. Britain had the U.S. at its back when it ceased being a power to be reckoned with. Should that day come for us, who will have ours?