Intelligence experts say the arrest of alleged terrorist Khalid Shaikh Mohammed is a major victory in the U.S.-led war on terrorism and a significant setback for al-Qaida.
U.S. officials describe Khalid Shaikh Mohammed as "a big fish" who effectively acted as al-Qaida's operations manager for the past several years, including plotting the September 11 attacks.
At the White House, presidential spokesman Ari Fleischer says intelligence intercepts involving Khalid Shaikh Mohammed were part of the reason U.S. officials raised the terror alert level for a time last month.
"Without getting into anything specific, as you know when the terror alert went up, it went up for a variety of factors," he said. "It is accurate to say that in several cases in those factors, there were ties to Khalid Shaikh Mohammed."
Intelligence experts say Khalid Shaikh Mohammed has the potential to provide counter-terrorism officials with a wealth of information about al-Qaida operations and membership.
"He knew virtually every al-Qaida cell in the world. He knew every operator in the world. He has been involved in virtually every attack for the past 10 years," said terrorism expert Neil Livingstone, who heads a security risk company in Washington D.C. called Global Options. "And a consequence, this is a significant blow for al-Qaida operationally. There is no one who has his breadth of experience who can step in behind him."
Another expert, Steve Emerson, told NBC's Today program that Mohammed is one of the few senior al-Qaida operatives that he would describe as irreplaceable.
"His arrest was the most devastating blow to al-Qaida since 9-11," he said. "It doesn't mean that they can't reconstitute. But the bottom line is, [he was] a nuts and bolts guy, CEO [chief executive officer] of the organization. [He is now] taken out and not very replaceable."
Pakistani agents who arrested Mohammed on Saturday also seized a potential treasure trove of communications equipment and documents that terrorism expert Neil Livingstone says could lead investigators to other al-Qaida members.
"The ISI [Pakistani Inter-Services Intelligence] and CIA operatives that went in found a variety of things including laptop computers, cell phones, other records and so on, that may indeed lead them to other terrorist cells and may lead them to [Osama] bin Laden himself," he said. "So they are going through that information now on a real time basis."
Neil Livingstone says the Mohammed arrest is good news in the long run but carries some risk in the short term. He says al-Qaida operatives planning further attacks could speed up their timetables in the wake of his capture.
"I think al-Qaida is going to be desperate right now to demonstrate that while they have been severely wounded with this capture that they are not out of business," he said. "And so they will be attempting to carry out some attacks someplace to say, 'Look it, we are still viable, we are still there and we still have to be taken seriously.'"
Mr. Livingstone also notes that counter-terrorism investigators are racing the clock, fully aware that any information they glean from the Mohammed arrest grows more dated by the hour.