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COIN warfare has very seldom been successful (in fact the the only example I can think of is Northern Ireland...and that was more a war for hearts and minds that was won by the Brits).
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Umm..really? It seems that you are not aware of a certain neighbouring country called India. We have succesfully crushed far more insidious insurgencies than Britain has had to face in the past few decades.
Remember the Punjab insurgency? If you don't remember, that itself is a testament to the thumping success we had in eradicating it. That was one of the finest COIN campaigns ever waged, against insurgents who were extremely well trained and well armed and fortified, and even had the sympathy of the local population and even in the army and police forces. And where are they today?
Remember the N number of insurgencies we faced in the North-east for decades? But once B'desh and Myanmar co-operated with us, we eradicated every one of them, and they exist merely in name today. We had to set up a dedicated counter insurgency school for the army and select police units, simply to tackle them. (The CIJWS in Mizoram.) Do you hear anything anymore about ULFA or Bodo national front or Naga seperatists or Mizo forces or any of them? Nope - we succesfully made them extinct.
Remember the Kashmir insurgency of the early 90s, when local Kashmiris aided by Pakistanis and Afghans (including your worshipped mountain men) and Uzbeks and Chechens and Arabs funneled there by Hamid Gul after the Soviet war took arms against the Union of India? Where is that insurgency now? It exists only in the minds of delusional Pakistanis. Today the RR has complete area domination of that state, and with campaigns like Operation Sadbhavana, they have won back the hearts and minds of Kashmiris, which was lost due to the criminal political games in the 80s. Indian Kashmir is more peaceful than any part of Pakistan.
So just because you have a hard time winning a COIN, don't draw the invalid conclusion that nobody can do it.