In fact, the people we're fighting are somewhat organized groups of common criminals. They operate embedded in the general population. The work of finding them and getting them locked up is much more like policing than like fighting a war. Sending soldiers into city neighborhoods to attack and defeat the 18 people that associate with terrorism (15 of them rather vaguely) is pretty much guaranteed to have a bad outcome (high civilian casualties; and next week that neighborhood has 38 people associated with terrorism living in it).