The inevitable question then is 'why could Bin Laden not find the means to attack 30 trains?' The answer it seems to me, must be Afghanistan, Iraq, the Horn of Africa and hundred other places where he is engaged without quarter by US forces. Resources, whether Jihadi or no are not infinite. They do not have some magical machine that allows them to be everywhere at once, to sustain losses yet grow. There's no free lunch, not even, and especially not for Bin Laden. If it were true that Islamism would shrivel faster were it pursued more passively, then pre-911 policy should have finished it by now. But what we empirically observe is that ignoring them allowed them to mount 911-scale attack. Hit them continuously and in four years they could scrape together enough to blow up a London bus and some subway trains.
I realize that this is not the unassailable proof that Patrick Belton seeks. I cannot provide that. But the practice of engaging an enemy on one front to weaken him on another has been tested from antiquity and is more natural than the alternative. The idea that fighting the enemy makes him stronger everywhere is a curious one and I've often wondered about the battlefield arithmetic that would make it possible. There are many who accept without question the proposition that the US Armed forces are being 'bled dry' in Iraq; that it has become over extended. They would accept, without reservation, the idea that using the US Army in Iraq would weaken it with respect to Korea. One Swedish researcher kept writing to me privately, 'proving' from all kinds of weird arithmetic that the USMC had been annihilated in Fallujah. Yet the very same persons will vehemently reject the idea that Al Qaeda can also be spread thin; that its cadres are subject to death as wastage; it is as if one set of natural laws operated for the Jihad and another for the blundering Americans. But mental honesty will compel us to accept that this can't be true: that the sun rises and sets on one man as for another: that if we thought about it really hard, everyone who lives peacefully in a Western city owes it to the men out on patrol tonight.(Emphasis mine)
I think he is absolutely correct.