As little as a week ago, Japanese news crews took several videos of large ISIS truck convoys in Syria, so you are wrong, in at least that case.
A convoy of trucks is hardly a "concentration of enemy fighters", and if you do not target them it does not matter how many there are anyway. Go back to my first claim about cannot win given current ROE. It is a lost cause, all we can do is limit US losses.
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And sadly, our military does not have a capability to take out a long convoy anymore anyway. Those days are over too.