The violence in Syria is spiking. 1,600 killed in the past week and 100,000 new refugees in the past month. After a year-and-a-half of violence, the UN reports that there are now more than 230,000 refugees, 1.2 million internally displaced persons, more than 2.5 million in need of humanitarian aid. Lakhdar Brahimi, the new UN/Arab League envoy called the violence “staggering.” Arab foreign ministers meeting in Cairo yesterday condemned Assad’s “crimes against humanity.”

So what have we learned over the past year-and-a-half?

First, despite all the complaints about the era of hyper-interventionism and the fears of R2P run amok, the default response by the international community — especially in complex environments — tends to be restraint. Libya appears to be the exception, not the rule. Neither the Obama administration nor the U.S. military wants any part of an intervention in Syria, the Security Council is deadlocked leaving the UN Secretary General, his special envoy, and the UN observer missions little leverage to alter conditions on the ground. Lots of talk, lots of posturing, but not much effect. In all of these regards, Syria is no different than Bosnia in 1992, or 1993, or 1994.

Second, major external military intervention likely would have significant costs — the conflict would likely escalate and lead to spill-over effects.

Third, limited (or no) intervention also likely will have significant costs — the conflict has escalated and does havespill-over effects.

In other words, the best argument for the current international response to date is that its the least worst option. That may well change…

…because, fourth, it looks like Assad’s regime is likely to become even more ruthless in the weeks and months to come. All of our indicators of the likelihood of mass atrocity events are present in Syria — a minority regime that is under acute military, political, and economic distress and one that has engaged in prior mass atrocities/genocide. It really can get worse.

Jon Lee Anderson’s reporting on the gruesome events ten days ago:

What happened in Daraya follows a pattern that is becoming chillingly routine. Last Saturday, after a withering five-day bombardment, Syrian Army forces entered Daraya and conducted a “mopping-up” operation. What occurred there can only be imagined, but the results are visible in YouTube videos that have been uploaded by activists in the days since then: hundreds of bodies piled up inside houses, in basements, and in a mosque. Many of the bodies were those of young men of fighting age, but there were also children there, and at least one toddler. Many of the victims, as in so many other body-dumps showing up in the environs of Damascus in recent weeks, bore the telltale signs of bullets to the head, fired close-up, execution-style.

Finally, while tipping points are difficult to predict, Assad’s escalation of violence against civilians, if unchecked will generate a new wave of political demands on the United States and others to do more — probably a lot more. A lesson from Bosnia two decades ago is that conflict duration coupled with spikes in intensity of violence against civilians eventually alter the political, moral, and strategic calculations about intervention. This is where the new era of intervention does come in. It may make generals nervous and realists uncomfortable, but global attitudes and norms on civilian violence have changed. We may not live in a world where “Never Again” is sufficiently strong enough to mobilize preventive or early response, but we do live in a world where “Enough is enough” eventually is triggered — my sense is that it’s just a matter of time…and lives.