“Militaries have learned the importance of following the laws of war and international conventions for the conduct of military operations,” he explained. “Even if the political authorities aren’t very sensitive about this, militaries are culturally attuned to this in terms of authorization needed.”
Exactly. Militaries fight wars. They have hands-on experience of the risks and consequences of war from the personal up to the political level. Which is why they have developed standards and protocols for combat.
Politicians like to play at war, but for all their War Rooms and Campaigns and Boots on the Ground, they have no idea what actual combat looks or feels like. They cause wars - it's always the military's job to get us out of them.
ISIL isn't a military - they're a gang. They're terrorists. They don't care about the long-term consequences of their actions; like a hormonal teenage boy, they're strictly focused on their now. They go with the frame of "the Apocalypse will take care of the future" but that's really just an excuse not to plan ahead (though, funny enough, the politicians within ISIL are developing complex governance structures - shouldn't that be God's job in their perspective, or are they assuming they're his proxy?)
Being tough is not the same as being organized. Aggression cannot succeed in the face of discipline.
There are meta-lessons in this, if anyone in position of authority can get it through their heads they aren't "history's actors" and learn from them.