(CBS)-- President Obama returned to the White House Wednesday morning from Afghanistan, where he signed a security agreement pledging U.S. support through 2024. Hours after he left Afghanistan, the Taliban set off a bomb in Kabul that killed seven civilians.
The president's visit came one year to the day after Navy SEALs killed Osama bin Laden. Hia terror group, al Qaeda, is now run by Ayman al Zawahiri, a physician and long-time bin Laden top deputy. So is al Qaeda still a threat? CBS News correspondent Bob Orr takes a look.
The world first met Dr. Ayman al Zawahiri as an angry young man, railing in English from a courtroom cell in Cairo. "We are here. The real Islamic front," he said back then.
That was 30 years ago when Zawahiri was an Islamic revolutionary in Egypt. He was arrested with hundreds of others for the assassination of Egyptian President Anwar Sadat. After three years in prison, Zawahiri left Egypt for a lifetime of terror.
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In 1998, he joined forces with Osama bin Laden. As al Qaeda's "Number Two," Zawahiri was at the core of every major attack, including 9/11. Following bin Laden's killing by U.S. Navy SEALs, Zawahiri seized control.
"He is as deadly a threat as we faced before," said Bruce Riedel, who spent three decades at the CIA chasing al Qaeda. He said Zawahiri wants to tighten his grip on the terror network.
"Zawahiri, to cement his authority, has to carry out terror," Riedel said. "He has to produce a significant terrorist attack which has his fingerprints on it."
"So to establish his credentials -- his standing in the terror world -- he needs to attack?" asked Orr.
"Sooner or later. You can't just talk about terror and expect to be regarded as a terrorist mastermind. You've got to orchestrate terror."
But Zawahiri's al Qaeda, centered in Pakistan, has been battered by relentless drone strikes and may not be capable of another large-scale attack. So Zawahiri has used a dozen audio and video messages since bin Laden's death to inspire strikes by al Qaeda affiliates and homegrown radicals within the U.S.
Juan Zarate, who was on the National Security Council of the George W. Bush White House, said Zawahiri's propaganda might help the U.S. find him. "Any time he pops his head up, like a prairie dog, he can be found or [a trace] back to him can be found."
"So the dilemma for Zawahiri is he needs to message to stay relevant. But when he messages, he becomes vulnerable?" Orr asked.
"That's right," said Zarate.
U.S. officials say if they get a clear shot at Zawahiri, they'll take it. Riedel said he suspects Zawahiri, like bin Laden, is hiding in a populated center somewhere deep inside Pakistan.
"Is it important to take Zawahiri off the battlefield?" Orr asked Riedel.
"Absolutely. This is a resourceful and smart guy, and it's important that we get him as soon as possible."
Zawahiri lacks bin Laden's charisma, and core al Qaeda is down to a few hundred members. But counterterrorism officials say it would be a big mistake to underestimate the Egyptian doctor.