The easiest way not to catch a thief or a bomber is to send in the Marines. This is what New York City is doing on their transport system. These guys can be spotted a mile away. They're slow. They are as likely to shoot perps or witnesses as interrogate them. They make everyone clam up within 20 blocks of the guns. They have weapons training, not detective training. They are the extreme opposite of undercover. They are a pure show of force - a symbolic display of power and nothing more.
The important thing about the New York Times article on the subject is that it doesn't even try to connect this military force in the subway to a real strategy. Why is it there? No answer.
Except "terrorism," of course, which apparently can cover for the most empty-headed but gun-toting activity. It used to be that you'd see armies patrolling the streets during periods of martial law under dictatorships, or in Mafia-controlled parts of Italy, or during the Red Brigade kidnapping days, or during urban rebellions. But even then the rule was the same: men with guns never uncover anything.
We bombed Afghanistan and did no detective work. Over five years later Osama is still at large. Afghanistan is once again the origin of 93 percent of the world's opium prodution, just like the good old pre-Taliban warlord days.
The M-4s will do just as much good in the NY subway. If a bomb goes off, these guys will be miles away. They will have no clue whodunit. They will know less that their bomb-sniffing dogs.
And so will we.