By Lionel Beehner

The gruesome images of American captives being beheaded by ISIS militants made front-page news. But the war in Syria has produced so many grisly images, I worry that our consciences can no longer be shocked.

To those like me who ponder what it would take to get our government to intervene for humanitarian reasons with force – having stood by idly last summer as an entire neighborhood of Damascus was gassed to death and an airplane full of passengers was shot out of the sky earlier this summer – I wonder if the culprit is our collective numbness to human suffering. Or maybe it’s the shrewdness of our enemies to creep up to the line of carrying out massacres without ever crossing over it. A case could be made that unlike, say, in the Balkans or Libya, there has been no “action-forcing event” in Syria.

But then thousands of Yazidi besieged on Mount Sinjar faced potential genocide at the hands of Islamist fighters and, lo and behold, we pounced. What 190,000 dead in Syria could not accomplish, the sheer act of preventing a pending massacre could. A similar explanation – to presumably avoid a bloodbath in Benghazi – informed NATO’s intervention in Libya. So maybe the lesson is: It takes a massacre to save a village?

Humanitarian interventions have long followed massacres, though in the past the victims were often Christians at the hands of non-Christians living “beyond the pale.” A massacre captures our collective attention on an issue (gun control) or a conflict (Syria’s civil war), even though we are not present, like no plea or petition can. It is the haunting memory of a rerun of such an event that propels otherwise stubborn politicians into action. Americans, however fleeting, are motivated by a “never again” ethos after such tragedies.

Take the massacre of 20 schoolchildren in Newtown, CT, which shook the national conscience and pushed Congress to finally debate – yet fail to pass any – sensible gun legislation. The real tragedy of such massacres is that the slow trickle of everyday gun violence, whether in urban neighborhoods on in war zones, goes untreated and uncovered. Only remarkable one-off events register these days.

We are creatures of habit. The preferred course of those uninvolved is to stand aside, or to look away. We have selective attention spans and short-term memories – a lethal combo for a country like ours asked to save the world.

The perpetrators are inevitably portrayed as “barbarous” or “sick,” not the work of rational or local actors. But this kind of reactive policy is neither rational nor reasonable, whether in response to a bout of mass violence on the street or to a civil war. A catch-22 of any massacre – whether a school shooting or campaign of genocide – is that its mere existence is evidence that more should have been done sooner. All massacres are preventable.

Several massacres have resulted from just bad policies. Arguably the massacres by ISIS rebels in Iraq could have been avoided had we not invaded Iraq in the first place (say liberals), or had we not pulled forces out so precipitously (say conservatives). Likewise, Newtown was a result of nonsensical gun laws. Srebrenica was a direct result of a flawed UN policy of creating so-called “safe havens,” that were neither safe nor havens. In many instances, such as in Rwanda, it’s often too little, too late. The same goes for 19th century interventions, which failed to prevent massacres. “European powers intervened too late, with too few troops and means or both,” writes Davide Rodogno in Against Massacre, citing examples in Greece, Lebanon, and Armenia.

Of course we know from recent history that a massacre does not always trigger a public outcry. A massacre is not just about quantity – there is also a qualitative component to it that matters. The Newtown massacre sparked more outrage than the Aurora, CO shootings because the victims were mostly innocent schoolchildren. Ditto the shooting in Ferguson, MO has triggered public outrage because of its racial component.

How we respond also matters. If President Obama had rammed through gun-control decrees in the wake of Newtown, it likely would have faced stiff resistance, and may have sparked mutinies across rural America. Similarly, if we were to unilaterally intervene in Ukraine to staunch the violence there, our legitimacy may be called into question. The most effective interventions are carried out in a collective fashion. This goes back to the 19th century Concert of Europe.

Don’t Europeans want those who committed this barbaric act, the downing of the Malaysian airliner, brought to justice? Or do they brush it off as an accident, a tragedy due to the fog of war, not to malice on the part of any rebel commander or Russian president. Maybe the world has just gotten better at forgiving, not just forgetting.

We are creatures of habit. The preferred course of those uninvolved is to stand aside, or to look away. We have selective attention spans and short-term memories – a lethal combo for a country like ours asked to save the world. We care about Joseph Kony one day, then forget about child soldiers in Uganda the next. We are galvanized by Boko Haram’s abduction of hundreds of schoolgirls and “bring our girls back” becomes a Paul Revere-like rallying cry. Yet most Americans have since forgotten about Boko Haram. When everything is a game-changer, nothing is a game-changer.

Even the downing of a civilian passenger airliner and the inexplicable deaths of 300 innocent passengers has faded from our collective memories. How are Europeans, especially the Dutch, not madder? Don’t they want those who committed this barbaric act brought to justice? Or do they brush it off as an accident, a tragedy due to the fog of war, not to malice on the part of any rebel commander or Russian president. Maybe the world has just gotten better at forgiving, not just forgetting.

Maybe, like the helpless doctor seen as cold-hearted to a dying patient, we are just becoming more aware of our own tragic inability to respond effectively. Maybe we are not growing more immune to suffering or to atrocities that shock the conscience but rather just realize that the cost of action with each new atrocity has increased.

Even as the Newtown shootings pushed America to finally confront its addiction to guns, nothing came of it. No such action-forcing event has occurred yet in Syria, not even the use of chemical weapons – after all, Americans knew that Saddam had gassed thousands of Kurds in Halabja in 1988 but did nothing. For civil wars, only a signal of a pending genocide raises the bar high enough to prompt an outside intervention. But dictators, terrorists, and gang leaders know that. So the lesson for Putin and Assad is clear: Kill slowly enough and you will be left alone.

Now ISIS has captured our collective imaginations – the image of an American journalist being beheaded replaying in our heads. The group may have overreached, having made the mistake of getting too close to Erbil and Baghdad, and threatening genocide of a persecuted minority. That was enough to trigger a U.S. intervention by air.

Yet, absent an action-forcing event –a massacre, a school shooting – we know that not much changes. We go about our business with backwards gun laws on the books. We go about ignoring Syria as the death count approaches 200,000. We ignore the steady drip-drip-drip of gang-related violence in places like South Chicago or Central America, until its kids show up at our border seeking asylum. Until it affects us directly. Even then, it is all we can do to look away.

[Photo: Flickr CC: Freedom House]

Lionel Beehner is formerly a senior staff writer at the website of the Council on Foreign Relations, where he was a term member. He is a member of USA Today’s Board of Contributors and is a PhD candidate at Yale, focusing on nonstate actors and the use of force.