As news of Osama Bin Laden's death changed from rumour into hard fact, and as celebrations (and relief) started to break out across the world, security analysts and experts began debating the effect that the terrorist's death would have on al-Qaeda and its terrorist affiliates.
While insurgent sources in Yemen told AFP that President Obama's success was "a catastrophe" for them, others downplayed Bin Laden's importance, the counterinsurgency expert Fredrick Kagan writing that the al-Qaeda leader's demise "does not, however, mark the end of the struggle against al Qaeda itself". Senior officials on both sides of the Atlantic have also warned about possible reprisals.
Past historical experience is also ambiguous about the impact of leadership decapitation. The classic example is the capture of the Shining Path leader Abimael Guzmán in Peru in 1992, which led to the subsequent surrender of 6,000 paramilitaries a year later. The terrorist movement, which at its peak controlled much of the countryside and was viewed as a grave threat to the central government, never recovered from these setbacks, splintering into two factions and retreating into the mountainous regions.
However, insurgent activity in Iraq did not peak until early 2007, three years after the capture of Saddam Hussein and a year after the death of Abu Musab al-Zarqawi, the then head of al-Qaeda in Iraq.
Research by Dr Andrew Roach of Glasgow University and the economist Paul Omerod suggests that the elimination of terrorist leaders has less of an effect than that of better-connected subordinates. Using network theory to simulate religious dissent in medieval Europe, they found that the most effective control techniques were the targeting of "hubs", individuals who were active in recruiting new members and running networks at a local and regional level.
In the case of the head of al-Qaeda, Roach contends that "Bin Laden's role as a hub was severely limited because of the difficulty he had in using any electronic communication".
John F McCreary, of the chief analysis office of KGS Security and author of the respected NightWatch Newsletter, believes that although a decapitation strategy is good for punishing individual terrorists, it is only one part of the solution. He warns that even small-scale groups usually have replacements lined up in advance, and notes: ''In Afghanistan the US has targeted mid-level insurgent leaders in specific districts, but the districts have never gotten more peaceful after the loss of the latest leader."
McCreary believes that counterterrorist policy should also focus on destroying the support infrastructure that terror groups depend on to supply and to renew themselves. This includes their funding, recruitment, supply lines and local support (the securing of which is also an important element of counterinsurgency theory). In his view, US commanders in Afghanistan need to spend more time on disrupting enemy logistics, especially those from Pakistan, which McCreary calls a "pipeline that the Taliban and their agents tap continuously".
However, even though Bin Laden's death may have little immediate impact on a purely tactical level, it provides justice for his victims in America and the rest of the world. It may also provide a reality check to those looking to imitate him. As Roach points out, "From being a talismanic, elusive fugitive he suddenly looks rather less heroic, and an already very loose-knit organisation loses one of its major unifying factors."