Ben Connable writes a fascinating piece for Foreign Affairs.
…insurgencies that involve more than one insurgent group generally last even longer and are more violent. Each group has its own constituency that has turned to fighting for its own reasons — each of which must be addressed to truly end the fighting. For example, three separate Angolan insurgent groups fought for independence from Portugal in the late 1960s. After the Portuguese colonial government collapsed in 1974, Angola became a battlefield among the insurgents; the fighting lasted into the 2000s. And at least 20 unique Iraqi insurgent groups fought U.S. forces in Iraq between 2003 and 2010. The insurgency there was especially bloody at its worst, and even today peace among all factions is far from assured.
Finally, insurgent groups that are voluntarily given sanctuary by another country win insurgencies — that is totally defeat the government they are fighting — twice as often as they lose. The value of haven is fairly self-evident: insurgents can use a secure space to train, organize, rest, refit, and, if necessary, hibernate. The loss of a haven, moreover, correlates strongly with defeat. Of those groups that had one and then lost it, only one in four went on to win its fight. This was certainly true for the Greek communist insurgents: after failing to seize control of Greece in the waning stages of World War II, the communists attempted to overthrow the Greek government. Until the middle of 1949, they enjoyed haven in Yugoslavia. Within one year of Yugoslavia closing its borders to the insurgents, the movement collapsed.
Major Ben Connable was always a thoughtful, incisive, amazingly intelligent, and thoroughly brave Marine Officer who made his bones on multiple tours in Al Anbar Province during the absolute worst of the insurgency. We ignore his counsel at our own peril.