Recent actions by the U.S.-led military effort against the Islamic State in Iraq and Syria (ISIS) has reignited a much-debated component of counterterrorism policy called "leadership decapitation," which aims to dismantle organizations from the top down by taking out high-ranking officials — thus leaving groups in a state of leaderless disarray. Within the last month or so, the Defense Department has announced it has killed ISIS's minister of war and the group's supposed No. 2, known by many various noms de guerre. "[W]e are systemically eliminating ISIL's Cabinet," Secretary of Defense Ashton Carter told reporters in March (using another acronym for the group).

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However, the decapitation strategy — which has been employed by the Obama administration via drone strikes and raids against leaders both in and outside areas of active hostilities — has produced little effect in beating back the strength of terrorist organizations. As Jenna Jordan, associate professor at Georgia Tech, wrote shortly after U.S. forces killed al Qaeda leader Osama bin Laden, "While bin Ladin's [sic] death was a major tactical victory for the United States, decapitation alone rarely results in the demise of terrorist organizations. Killing bin Ladin [sic] may destabilize al-Qa'ida temporarily, but his death is unlikely to be a significant blow to the organization," noting that such a decentralized organization with many regional affiliates makes decapitation difficult to glean strategic successes.

Al Qaeda's affiliates have continued, and in some cases have increased their attacks and influence in their regions, despite years of counterterrorism intervention by the U.S. Al Qaeda's Yemen affiliate has capitalized on that country's civil war to capture and control large swaths of territory even after the U.S. killed its leader, who was also al Qaeda's general manager, last summer. His death had seemingly little effect, given that the group quickly replaced him.

In Somalia, al Qaeda's franchise, al-Shabaab, has continued both its domestic and cross-border attacks unabated. "Unfortunately the deaths of [al-Shabaab's top leaders] and a number of senior al Qaeda and Shabaab leaders at the hands of the US has done little to disrupt Shabaab's command or control," Bill Roggio, senior fellow at the Foundation for Defense of Democracies, wrote in The Long War Journal. "The jihadist group has been waging an effective insurgency and still controls territory in Somalia despite the fact that the US began targeting Shabaab's leadership beginning in late 2006." To make matters worse, the acting Afghanin minister of defense, when characterizing al Qaeda's strength in his country, called the group "very active" and a "big threat."

But as Secretary Carter noted when responding to criticism of decapitation efforts:

[S]triking leadership is necessary, but as you note, it's far from sufficient ... leaders can be replaced. However, these [ISIS] leaders have been around for a long time. They are senior, they're experienced, and so eliminating them is an important objective and it achieves an important result. But they will be replaced and we'll continue to go after their leadership and other aspects of their capability. So I would say it's necessary. It's not sufficient, but it's important.

And as Col. Steve Warren, spokesman for the anti-ISIS coalition, said in April: "[A]ny organization that has lost ... its most senior leaders in a span of 30 days is going to suffer for it." Warren added that leadership strikes "[create] confusion, [create] paranoia," an "organization ... turning in on itself," and this ultimately "weakens this enemy."

Decapitation strategies, according to two researchers, however, can lead to even more violence due to the inexperience of mid-level leaders taking the reins. "When their leaderships are debilitated in a successful strike, militant groups become far less discriminate in their target selection by redirecting their violence from military to civilian targets," Max Abrahms of Northeastern University and Jochen Mieraub of the University of Groningen wrote.

The same fate came of ISIS's predecessor organization, al Qaeda in Iraq (AQI). The death of AQI's military and spiritual leader, Abu Musab al Zarqawi, death "caused an inevitable sense of satisfaction at all levels of command," Sean Naylor recounted of U.S. military leaders in his book "Relentless Strike: The Secret History of Joint Special Operations Command." Naylor noted that violence by AQI under its next leader, Abu Ayyub al-Masri, increased substantially, leading top U.S. officials to conclude they "'had killed Zarqawi too late.'"

While Americans did not see immediate effects on the battlefield, the organization did begin to fracture over time losing public support due to poor leadership and mismanagement. "[T]he man who ran the Islamic State in its first year, Abu Ayyub al-Masri, was an abject failure," Brookings senior fellow Will McCants wrote in his book "The ISIS Apocalypse: The History, Strategy, and Doomsday Vision of the Islamic State."

The U.S., at the time, continued its offensive to quell Iraq's violence — with the help of Sunni tribes whose support to fight Masri's group was bought by the U.S. — eventually degrading the Islamic State of Iraq/AQI, though not defeating it. "The 2007 tribal uprising against AQI, known as The Awakening, undoubtedly damaged and constrained the group, but those defeats were not nearly as decisive as conventional wisdom holds," wrote Brian Fishman, fellow at the New America Foundation. "Rather than destroy AQI, pressure from U.S., Iraqi, and tribal forces pushed the group from Iraq's Sunni heartland north to the contested northern city of Mosul, which was never pacified (nor covered by American media) like other areas of Iraq." ISI/AQI was then able to regroup and metamorphose into its current incarnation.

Despite how leadership decapitation affected AQI in the past, the group is now much stronger and much larger boasting a global reach. As Carter said, decapitation alone is "far from sufficient," just as with other terrorist organizations. (Warren, the Operation Inherent Resolve spokesperson, did note that the coalition is hitting mid-level leadership as well).

"Even still, the winnowing of the uppermost echelon of the organization doesn't mean the imminent end of ISIS, or even the beginning of the end," Hassan and Michael Weiss, authors of "ISIS: Inside the Army of Terror," wrote recently. "For a decade, since the killing of its top leaders in 2006 (al-Zarqawi) and 2010 (Abu Omar al-Baghdadi and his war minister Abu Ayyub al-Masri), ISIS has adapted to changing wartime exigencies (the al-Anbar Awakening, the 'surge,' the U.S. military withdrawal, the Syrian revolution) and regrouped." After all, one of group's popular slogans translates to "enduring and expanding."

This piece was corrected on April 27, 2016 at 12:10 p.m.

Pomerleau is a freelance journalist based in Washington covering politics and policy. Follow him @MpoM24.