@RH - Ah...the old insult is renewed: "That [named thing] is dumb as a box of rocks."
I find myself agreeing with the dissent on this comment train. This study doesn't appear to have "taught" us anything we haven't "learned" before. It's scientific value seems dubious at best, respecting the somewhat majority opinion here that suggests that the science here was valuable at least for science's sake.
Respecting @Tam's comment, yes okay so we can agree that tactical value is just about nil, but I'm not reading any strategic value here either. The conclusions ought to provide some manner of insight, but it's only confirming what is already generally intuited by battle managers from the action reports. Now while this has "some" value, and is scientifically valid as a result, how does it help? It...really doesn't.
Yeah, screw cost-benefit. If it were privately funded, I'd care very little. But, if this was gov't/military funded research, then I *facepalm*. This research isn't going to tangibly help insurgent-facing personnel "learn" how to better defend themselves and reduce casualty rates. And, it probably has diverted resources that might have otherwise been employed to do precisely this.
You want to be able to start to answer the "why?" and the "how?" questions to get insight valuable to defending insurgent-facing folks.
Setting this matter aside, and thus departing the topic, one way (for the US military) to get some positive results almost immediately would be to finally withdraw from these conflict zones where our forces are being exposed to insurgents. Our past interference is cited as reason justifying further interference to "fix" the situation precipitated by that past interference.
But this sort of mentality tends to lead managers right off a cliff. It creates a locked-in mentality that is generally only aborted by catastrophic loss or complete depletion of resources (we're fresh out of men, money, equip., will, rule-of-law, political support, etc.). And...well that's precisely the strategy the insurgents are aiming for...running out the clock on us. The only thing this study is saying strategically is that they're getting more efficient at that aim.
I like @NobodySpecial's insight regarding the N. Ireland conflict. This "winning hearts and minds" strategy by imposing external force generally _as_ lethal and oppressive as that threatened by insurgent groups is and has been only successful at piling up bodies on all sides.
A fundamental shift is required, it starts by withdrawing military abroad to defend the home territory only, as it was originally intended for.
What would follow after this step is a whole other topic entirely (so I stop now). But research into it could have _real_ value for this whole insurgent problem, as it goes right to the heart of why insurgent groups rise in the first place. And at any rate, practical experience (two semi-permanent conflicts running longer than any single war in the history of the USA, no (real) end in sight, and the genesis of a third) has more than shown that a radical shift of strategy is warranted, as the cost of continuing the present course will be pyrrhic now even assuming the best case.
(Sorry about the OT comments, but the topic just naturally leads me to 'em.)