I’ve somehow missed the fact that Barbara F. Walter, who fifteen years wrote “The Critical Barrier to Civil War Settlement,” a seminal work in helping us understand the conflicts that were suddenly on the Western radar screen after decades of being overshadowed by the Cold War, launched a blog called Political Violence @ a Glance over a year ago.

If her latest post, “The Four Things We Know About How Civil Wars End (and What This Tells Us About Syria),” is any indication, it’s an outstanding resource.

She makes four key points:

1. Civil wars don’t end quickly. The average length of civil wars since 1945 have been about 10 years. This suggests that the civil war in Syria is in its early stages, and not in the later stagesthat tend to encourage combatants to negotiate a settlement.
2. The greater the number of factions, the longer a civil war tends to last. Syria’s civil war is being fought between the Assad government and at least 13 major rebel groups whose alliances are relatively fluid. This suggests that Syria’s civil war is likely to last longer than the average civil war.
3. Most civil wars end in decisive military victories, not negotiated settlements. Of these wars governments have won about 40% of the time, rebels about 35% of the time. The remainder tend to end in negotiated settlements. This suggests that the civil war in Syria will not end in a negotiated settlement but will rather end on the battlefield.
4. Finally, the civil wars that end in successfully negotiated settlements tend to have two things in common. First, they tend to divide political power amongst the combatants based on their position on the battlefield. This means that any negotiated settlement in Syria will need to include both the Assad regime and the Islamists, neither of whom is particularly interested in working with the other. Second, successful settlements all enjoy the help of a third party willing to ensure the safety of combatants as they demobilize. This means that even if all sides eventually agree to negotiate (i.e., due to a military stalemate or increasingly heavy costs), it’s unlikely that any country or the U.N. will be willing to send the peacekeepers necessary to help implement the peace. The likelihood of a successful negotiated settlement in Syria? Probably close to zero.

The call to “do something” in situations like this are easy and understandable. But the evidence suggests that there’s no acceptable “something” to be done.