Have you wondered why the Iraqi Army, which the U.S. spent billions manning, equipping, and training, was such a washout? I have, and it isn't because they're Arabs - heck, the ISIS guys who beat them are Arabs too.
The American Conservative has a good article by Kelley Vlahos on this subject. She spends most of her time commenting on their corruption, which is cultural and likely shared with the opposition. I suspect the following is more like it, Vlahos quotes the opinions of Maj. Donald Vandergriff (Ret.), who has done contract work training Afghan security forces:
He said the U.S. made the same mistakes in Afghanistan and Iraq that it did in Vietnam over 40 years ago. “I’ve said all along, we keep trying to make these forces in our own image,” he said, and “they don’t take ownership because the system was forced upon them.”Decades ago we saw the people of Guam blindly following a model they'd learned from the U.S. Navy even though the Navy no longer ran things and it no longer made sense to do it the bureaucratic Navy way. You can be darn sure the ISIS forces are doing what comes naturally to locals, not going through the motions of trying to imitate U.S. troops without truly understanding why.
The technology, the logistics, the modern air power, the intelligence—were and are all foreign to them. U.S. trainers come and go on short rotations, and there is no consistency, no ability to learn the foreign culture and understand the gaps. “Again we have to say, what kind of force would these people buy into? What kind of military can they afford and accept? Instead we force our own grand, narcissistic vision.”
The local idea of military tactics, and organization, probably has more in common with an Apache war party than with a U.S. combat unit - very tribal.