While the major argument for invading Iraq was the WMDs, now that we're there, a common argument now is the "flypaper theory" - we're attracting terrorists to Iraq so they won't attack somewhere else. As I wrote before, I'm not a big fan of that theory for several reasons.
One: Isn't that basically helping to train terrorists in the first place? The ones who come to Iraq, learn, and get out over a porous border we still have trouble closing are now experienced. It COULD happen they would have learned somewhere else, but it COULD also happen that they learned their skills in Iraq. Regardless, we know that the attacks are Iraq have shown some signs of "professionalism", if you will, which means somebody's learning or teaching something. The flypaper theory only works if you kill each and every terrorist down in Iraq and not let them get out - something we haven't been able to accomplish.
Two: This argument cuts both ways - you can't say that any attempt that happened in Iraq would have happened somewhere else had we not been in Iraq. In other words, if a car bomb goes off in Baghdad, you can't say that bomb would have gone off in Cartagena or London or Paris or New York if we weren't in Iraq and claim the flypaper theory. It's not a fact that bombing would have happened but in a different place, it's a guess, and one with no way to prove. To put it another way, proponents of this theory seem to feel that there is only X terrorist acts, so an act in one place removes the act from somewhere else. But of course a new attack just adds 1 to X, it doesn't exchange one place for another. So the simple fact of terrorist acts down there doesn't mean they were moved from one place to another - it just means there were terrorist acts down there. This also applies to the other end of the scale, of course - the terrorist attack in London may have happened if we weren't in Iraq anyway, so we can't say that's a sign the flypaper theory is wrong. But either way, this argument doesn't hold up.
Three: This may just be me, but it seems we're saying we using soldiers as bait, basically. Color me naive, but this is a little bald-faced for me to swallow. "Hell, we want people to be killed, including our own soldiers, so we can get them down there!"
I think this theory has many problems with it, and don't accept it as any kind of justification.