The Iraq Syndrome has played a role in U.S. politics for nearly a decade. As I wrote in 2005, public support for the war in Iraq followed the same course as for the wars in Korea and Vietnam: broad acceptance at the outset with erosion of support as casualties mount. The experience of those past wars also suggests that there was nothing U.S. President George W. Bush could do to reverse this deterioration -- or to stave off an "Iraq Syndrome" that would inhibit U.S. foreign policy in the future.

In recent years, the Iraq Syndrome has indeed colored U.S. foreign policy -- from its timorous “lead from behind” approach in Libya (where American forces have since been withdrawn due to the ensuing civil war) to its cheerleader (vast proclamation and half-vast execution) approach to the Arab Spring. The Iraq Syndrome could be seen in fullest flower last year, when U.S. President Barack Obama, supported by Republican leaders in Congress, initially signaled that he would bomb Syria for its apparent use of chemical weapons and then backtracked when his plans were met with intense hostility by a public determined not to be dragged into another war in the Middle East -- even though no American lives were likely to be lost in the exercise and even though U.S. Secretary of State John Kerry assured Americans that the bombings would be “unbelievably small.”

Just over a year later, the Iraq Syndrome has found a new application, as it happens, in Iraq itself. It has been obvious for some time that last decade’s Iraq War would spawn a “let’s not do that again” attitude. For example, a poll in relatively hawkish Alabama in 2005 -- even before the Iraq War got really bad -- found that only a third of the respondents agreed that the United States should be prepared to send troops back to Iraq to establish order if a full-scale civil war erupted there after a U.S. withdrawal. The percentage today would likely be considerably lower, even as Iraq teeters on the brink of collapse.

It’s a true debacle. However, as I suggested in my Foreign Affairs article and in later commentary, Americans are quite capable of taking foreign policy debacles in stride. When sending policing troops to war-torn Lebanon in 1983, U.S. President Ronald Reagan grandly declared that the conflict there somehow was “a threat to all the people of the world, not just to the Middle East itself.” The public accepted his decision, but it then supported -- indeed, impelled -- his abrupt withdrawal after a terrorist attack killed 241 of those troops. It then handily re-elected him a few months later.

Similarly, the spectacular failure of the U.S. position in Vietnam in 1975 was used by the man who presided over it, U.S. President Gerald Ford, as a point in his favor in his reelection campaign the next year. When he came into office, noted Ford, the United States was “still deeply involved in the problems of Vietnam, [but now] we are at peace. Not a single young American is fighting or dying on any foreign soil.” His rather bizarre declaration in defense of debacle may not have helped him in the election, but it didn’t hurt him either.

Americans have never been very supportive of putting American troops in harm’s way for purposes that are primarily humanitarian. As with the wars in Korea and Vietnam, they did buy the war in Iraq for a while because they saw it, like Afghanistan, as a response to 9/11 -- a direct attack on the United States.

Now, however, with the Iraq Syndrome in force, political leaders have done lot of tough taking, but no one seems willing to advocate sending in troops. Supporters of doing something of that sort would have to convince the public that it would be necessary to prevent a direct attack on the United States.

On Sunday, Senator Lindsey Graham (R–S.C.) tried his hand, explaining that an Islamist takeover of parts of Iraq would provide terrorists with a “staging area” from which they would carry out “another 9/11.” Former U.S. Ambassador to Iraq Ryan Crocker issued a comparable warning. Obama has made similar statements, and the Washington Post’s David Ignatius has speculated ominously, if vaguely, that a newly established terrorist “safe haven” -- as opposed to the ones that have existed in the area for years -- “could soon be used to attack foreign targets.”

However, 9/11 remains an aberration, not a harbinger. No terrorist act in history has visited even one-tenth as much death and destruction, even ones launched during civil wars, when terrorists have had plenty of time and space in which to stage them. It is thus hard to follow the logic of Senator John McCain (R–A.Z.), who opines that having Syria and Iraq in extremist hands would represent an existential threat to the United States; that is, that if Syria and Iraq acquire reprehensible new leaders -- different from the reprehensible ones they have had in the past -- the United States will cease to exist. This sort of extravagant threat-inflation has been applied frequently since 9/11, and it has gone amazingly unchallenged.

But such alarmism has become less common in recent years, and getting it accepted seems to be increasingly difficult, in major part because it was used to justify two disastrous wars as well as spillover violence in Pakistan. These have led to destruction at least 40 times greater than witnessed on 9/11 and have resulted in the deaths of twice as many Americans as were killed that day -- and more deaths overall than at Hiroshima and Nagaski combined.

In other words, American foreign policy at its most active over the last dozen or so years, routinely decorated with extravagant alarmism, has been an abject failure. If those who established and maintained this disastrous record have, at long last, lost all credibility, we may all be the better for it.