In the Democratic presidential debate Monday night, the candidates were united on the need for the United States to withdraw from Iraq. But most were equally convinced about the need to intervene in Darfur. Sen. Joseph Biden was out front on this issue, arguing that the United States should take military action wherever it can make a difference in humanitarian crises. We should intervene in Darfur, Biden intoned, “because we can.” Such an attitude suggests that the Democrats have learned little from the Iraq debacle. They are not against elective wars — interventions that have little or no connection to the security and well being of the United States — as a matter of principle. Instead, they appear merely to be against Republican elective wars that go badly.

Even worse, they seem unwilling or unable, or both, to think through the medium- to long-term ramifications of military action, generally. This is worrisome when it involves people aspiring to be the commander in chief of our military.

The suffering in Darfur cries out for action, but it is not clear that it calls for military action, much less that U.S. troops should lead the effort. There are dozens of countries that have far greater tangible interests at stake in Darfur than does America, and many of these countries also possess the capacity to deploy forces there. If there is a serious military intervention, they should be expected to step forward long before the United States does.

AMERICANS WOULD BE WELL-ADVISED TO CONSIDER THE LARGER LESSONS OF IRAQ. No one disputes that the situation in Darfur is a humanitarian tragedy, but it is dangerous folly to assume that a U.S.-led military intervention would solve the problem. It might even make a horrible situation even worse. Let’s remember that most supporters of the invasion and occupation of Iraq believed it would be, in the words of former Reagan administration official Kenneth Adelman, “a cakewalk.” It has proved to be anything but that.

True, military action does not always turn out as badly as in Iraq. We have occasionally gotten lucky. The 1991 Persian Gulf War claimed far fewer American lives than most experts had predicted. The relatively low cost, and the seemingly decisive victory, led President George H.W. Bush to crow that the country had “licked the Vietnam syndrome” once and for all. In the shadow of his son’s adventure in Iraq, that claim becomes increasingly dubious.

There are many other cases in which interventions turn out to be longer, bloodier and more intractable than anticipated. The Iraq mission certainly merits that label, as did the Vietnam War four decades earlier. So too did the intervention in Lebanon in 1982–83 and the mission in Somalia in 1992–93, both of which began humanitarian relief efforts and morphed into nation-building crusades in the midst of multi-sided civil wars. The former culminated in the bombing of the Marine barracks and the deaths of 241 Marines; the latter collapsed after the firefight in Mogadishu that left 18 Army Rangers dead.

In short, it is reckless to launch military action without some understanding of the anticipated costs. It is irresponsible to unleash the military without a clear objective. It is short-sighted to assign this objective in the first place without an honest assessment of the likelihood that the military can achieve it. It is unconscionable to launch a war of choice without some reasonable expectation that the post-conflict situation will be a dramatic improvement over that which came before. That is what Colin Powell was talking about when he told President Bush in August 2002, “You break it, you own it.”

Another prominent military leader had similar concerns. As he led the 101st Airborne Division in Iraq in March 2003, Gen. David Petraeus could have been forgiven a bit of triumphalism. Yet Petraeus was haunted by one nagging question: “Tell me how this ends?”

Petraeus understood that it is easy to start wars but extremely difficult to end them. This principle applies to wars started by Democrats, as well as to those started by Republicans. Can the candidates on the stage Monday night answer Petraeus’ “tell me how this ends” question with respect to Darfur? Can they answer it with respect to war with Iran, or other potential conflicts?

We have wasted blood and treasure in Iraq, and that is a great tragedy. It will be an even greater tragedy if we blunder into another well-meaning intervention without carefully thinking through the possible consequences.