There's a classic military technique for determining where to strike an enemy. You want your target to be something the enemy needs, something the enemy loves, and something that's not easily replaced.
We've been planning aerial bombing raids using this formula for decades now. So it shouldn't surprise us that our enemies do the same. They like to strike us in a manner that is sure to make us mourn, make us bleed, and weaken us.
Thinking about the methods that our enemies might use against us and the targets they might choose is an exercise that we don't undertake often enough. This kind of "red cell" exercise has two purposes: It keeps the threat present and real in our minds and it helps us determine what targets we need to harden.
The following is a quick look at where and how some of the leading experts on terrorism believe our enemies may strike. It's in no particular order because each scenario is a nightmare, and how do you rate a nightmare?
No crime wave in the last decade instilled more fear than the Beltway Sniper attacks. For three weeks in October 2002, the entire Washington, D.C., metropolitan area was terrorized by random sniper attacks. People were shot as they walked into restaurants, as they walked out of stores, and as they pumped fuel into their cars. As the death toll mounted, climbing to 10 victims, people stopped leaving their houses, people literally ran into stores, and people crouched behind their cars as they filled their gas tanks.
All of this havoc was created by two men who had turned the trunk of a 1990 Chevy Caprice into a mobile sniper hide. This tactic has since been copied by Islamist snipers in Iraq to terrible effect on our troops. It's not much of a reach to think that some of these terrorist snipers can't wait to use their marksmanship skills here on the soil of the Great Satan.
The terrorists have as much access to the news as the rest of us. They know about Virginia Tech and they surely know about Fort Hood. So whether it's lone wolves or groups of armed men, we can bet that the terrorists plan to hit us with active shooters.
Of course the nightmare scenario here is a Mumbai-style attack with multiple shooters going mobile through an urban area. For the Mumbai attack, the shooters arrived by boat. The principle reason for using water for the insertion was so they could bring their weapons into India. So don't think that just because your city isn't on water that it's necessarily immune to a Mumbai-style assault.
Responding to a Mumbai-style "swarm" attack will tax the resources of even the largest department. Imagine all of the calls to 911 from a panicked populace. Imagine all of the traffic jams and the chaos. It will be a mess. And every urban department needs to have a plan to deal with such an attack.