DOD: War against al Qaeda could last decades

While American and allied forces have taken out much of the terror group's senior leadership, including al Qaeda chieftain Osama Bin Laden, the war on al Qaeda is far from over. 

"In my judgment, this is gonna go on for quite awhile," Michael Sheehan, head of the Pentagon's special operations and low-intensity conflict directorate, told the Senate Armed Service Committee on Thursday. 

When panel member Sen. Lindsey Graham (R-S.C.) asked Sheehan exactly how long that could be, he replied: "I think it's at least 10 to 20 years." 

Sheehan's comments echoed those by Gen. Joseph Dunford, head of all U.S. forces in Afghanistan, when he was asked on whether the Taliban can be completely defeated in the country. 

"My assumption is that the [Afghan] insurgency will still exist after 2014,"  Dunford told ABC News in April. 

"The conditions are not yet set for a stable and secure Afghanistan in the long-term," he added.

Graham's questions on Tuesday centered around whether it was time to change the rules of war governing the fight against al Qaeda, known as the Authorization of the Use of Military Force (AUMF).

Passed in the days immediately after the 9/11 attacks, the authorization law gave military and intelligence agencies wide leeway to pursue al Qaeda.

From the U.S. terror detainee program to armed drone strikes, the rules have allowed American forces to kill most of the terror group’s senior leaders, including Osama bin Laden.

But more than a decade after the law was approved, White House counterterrorism officials have used the law's mandates to expand the scope of those operations far beyond hunting down the perpetrators of 9/11. 

The rules of war passed by Congress after 9/11 allowed the U.S. "to be at war with al Qaeda" no matter how long that war lasts,  Robert Taylor, the Defense Department's acting general counsel, told committee members. 

"That organization ... has associated forces, forces that have joined with that organization," he said. "And, yes sir, we are authorized to attack ... those who have chosen to associate with that organization." 

Those laws "provides the authority to take the fight to AQAP just as it provides the authority to take the fight to al Qaeda senior leadership," he added.