This is a long article, but the logic behind it is useful in challenging the assertions in recent COIN studies that allegedly identified the behaviors and tactics of successful COIN operations.

As with the torpedo problem, the top brass explained what they knew, and the Panel presented the problem to Wald and his group. How, the Army Air Force asked, could they improve the odds of a bomber making it home? Military engineers explained to the statistician that they already knew the allied bombers needed more armor, but the ground crews couldn’t just cover the planes like tanks, not if they wanted them to take off. The operational commanders asked for help figuring out the best places to add what little protection they could. It was here that Wald prevented the military from falling prey to survivorship bias, an error in perception that could have turned the tide of the war if left unnoticed and uncorrected. See if you can spot it.
Survivorship bias also flash-freezes your brain into a state of ignorance from which you believe success is more common than it truly is and therefore you leap to the conclusion that it also must be easier to obtain. You develop a completely inaccurate assessment of reality thanks to a prejudice that grants the tiny number of survivors the privilege of representing the much larger group to which they originally belonged.
All we know of the past passes through a million, million filters, and a great deal is never recorded or is tossed aside to make room for something more interesting or beautiful or audacious. All we will learn from history reaches us from the stories that, for whatever reason, survived