Bruce Hoffman has a sobering piece in West Point's Counterrorism Sentinel arguing that Osama bin Laden's death won't be the end of al Qaeda, because terrorist organizations tend to be resistant to losing their leadership:
In this respect, history unfortunately may be on al-Qa`ida's side. Decapitation has rarely provided a decisive end to a terrorist movement. During Algeria's war of independence in the late 1950s, for instance, the French apprehended the National Liberation Front's (NLF) core leadership cadre. Yet, they found that the FLN was much more networked than had been imagined and therefore resistant to even the decapitation of its entire leadership. As the French counterinsurgency theorist and practitioner par excellence David Galula observed shortly afterward, the “five top leaders of the rebellion, including [Ahmed] Ben Bella, had been neatly caught during a flight from Rabat to Tunis. Their capture, I admit, had little effect on the direction of the rebellion, because the movement was too loosely organized to crumble under such a blow.” The FLN, of course, went on to triumph and attain independence for Algeria just four years later.
Similarly, in 2004 the Israelis delivered a seemingly devastating one-two punch against Hamas: killing the equivalent of Bin Ladin and his deputy, Ayman al-Zawahiri, when they assassinated in succession Shaykh Ahmed Yassin, the founder and leader of Hamas, and then a month later Abdel Aziz Rantisi, his deputy and successor. Yet Hamas is today stronger than it was seven years ago as a new generation of militants continues to prosecute its struggle against Israel.
I suppose the key thing is here is that removing the leadership of terrorist organizations rarely works when the conditions that produced them in the first place continue to be prevalent, such as conditions in Gaza or France's continued occupation of Algeria. This is why I believe the U.S. should strive to reduce its footprint in the Middle East, North Africa, and Central Asia, and why it might be time to finally leave Afghanistan.