President Obama is fond of saying he was elected to “end” wars, not start them. He clearly is tapping into Americans’ well-known weariness of wars and sees himself as merely carrying out their will.

But there’s a problem. Americans may indeed be war-weary (although how much may be exaggerated), but that only means they assume Mr. Obama’s policies will actually end the wars and bring peace.

By this measure, the president’s “no war, no way” policy isn’t working. Clearly, Iraq is exploding into a major new war that our continued presence could possibly have prevented. By the same token, our precipitous withdrawal from Afghanistan may result in the Taliban’s return to power.

President Obama is banking on the gamble that we can walk away without any damage to our security. After all, this is the essence of “ending” a war versus actually winning it. So long as we’re not dragged back into the fighting, the thinking goes, there’s really no skin off our nose if our side loses. Otherwise we’d be doing everything in our power to make sure that doesn’t happen.

Clearly this is not the case. By withdrawing from Afghanistan on a timetable dictated by politics, not military conditions on the ground, we are leaving our friends to their own fate. This implies not only that the original purpose of fighting the war — i.e., preventing safe havens for terrorists who can kill us — was not worth it, but also that all our sacrifices could be in vain.

The president seems to believe the fighting in Iraq and Afghanistan cannot deteriorate enough to drag us back in. But what if he’s wrong? What makes him think a reconstituted Taliban, either partially or throughout the country, won’t be a magnet for future terrorists plotting another strike on our homeland?

What would we do if there were another 9/11? Launch a few cruise missiles, as President Clinton did in 1998 after our embassies in Kenya and Tanzania were attacked, which did nothing to stop the attacks on New York and the Pentagon?

Or what if a new terrorist regime is carved out of Syria and Iraq by the Islamic State of Iraq and Syria (ISIS)? That could lead to a full-fledged regional war, possibly involving Iran, Turkey, Saudi Arabia and even Jordan and Israel. Are we to stand by as oil prices go through the roof and terrorist plots on us are hatched from there as well?

As the old saying goes, an ounce of prevention is worth a pound of cure, and in Iraq and Afghanistan we are failing mightily in the prevention department. Make no mistake: It was Mr. Obama, not President George W. Bush, who failed in that particular duty. When Mr. Obama entered office in 2009, Iraq was in fairly good shape. The war was not yet over, but if we’d maintained a residual military force for training and advising Iraq’s security forces and for counterterrorism missions, as Mr. Bush had planned, the ISIS threat would have been mitigated. And Prime Minister Nouri al-Maliki would not have been as dependent on Iran.

We are left with an escalating civil war in Iraq that could very well have been prevented. President Obama’s shortsighted focus on pulling out of Iraq not only left a power vacuum now being filled by Iran and Islamist terrorists; it also risks a greater conflagration that pales in comparison with what we are now seeing.

We’ve watched this movie many times before. After World War I, war-weary Americans thought merely “avoiding” wars would stop them. Hitler showed them differently. We thought we could walk away from Vietnam, only to witness the “killing fields” of Cambodia.

Once again we seem to be learning the wrong historical lessons. For America, it’s not merely “staying out” of wars that prevents them. It’s a strong engagement on the ground with training, diplomacy and military support to deter attacks on us and our allies.

 - Kim R. Holmes is a distinguished fellow at the Heritage Foundation.