Watching Rumsfield and the other grownups testify before the 911 Commission. It's a refreshing revelation about how complicated things are and why simple answers are not to be found.
Former Senator Bob Kerrey is right. We should have declared war against Osama and his organization in 1993 or 1998 or 2000. I can see why the Clinton administration didn't, though. We had the wrong military force structure then to fight such a war. According to the testimony I heard at the hearing, the choices for pursuing Al Qada were either lob a few cruise missiles or invade with too light forces or invade with too heavy forces.
No effort was made by the Clinton administration to change the force mix to give us more options. Instead, when Rumsfield took over at Defense, he started pushing for a more agile military that would allow a "just right" force to be applied. While being carped at by the critics of why it took so long to respond to the USS Cole attack, Rumsfield could have said "it took that long for the bureaucrats to take me seriously" and for the planners to get it together. He had already ruled out (as apparently so had the Clinton admin) the futile use of cruise missiles.
And, as wiser heads have already said, can you imagine the howling that would have arisen if we had suddenly invaded Afghanistan in pursuit of OBL? The current anti-war (anti-Bush) crowd would have really been after the "illegitimate" president.
Not to mention the problems caused trying to sustain a force on hostile ground with no friendlies nearby. The Germans got pounded by the Russians when the Luftwaffe couldn't keep the ground forces supplied... and if we had tried to do it from ships at sea, it would have been a logistical nightmare.