SpyTalk

And four months ago, CIA Director Michael Hayden said that, while al Qaeda had plenty of punch left, it was "essentially defeated in Iraq and Saudi Arabia and on the defensive throughout much of the rest of the world, including in its presumed haven along the Afghanistan-Pakistan border."

But the attack early Wednesday on the U.S. embassy in Sa'ana,  carried out by a large team of operatives in military fatigues, leaves no doubt that the terrorist movement still has a capability to shock.

A group that calls itself Islamic Jihad of Yemen claimed responsibility for the attack, which left 16 dead, none of them Americans. 

U.S. officials could not verify the claims of responsibility, but a State Department official told Reuters the attack "bears all the hallmarks" of al-Qaeda

State Department spokesman Sean McCormack told reporters the attackers apparently sought to breach the embassy's walls.

Their aim might have been to overpower the embassy guards, take hostages and influence the American presidential elections, as Iranian militants did in Tehran in 1979, said a retired spy familiar with the area. He asked that his name not be used because all the details of the attack were not yet known. 

It seems like the team was large enough to do more than just blow something up.

Tactically it would have been interesting: Think Tehran-like embassy takeover, in the middle of a presidential election, hostages being executed on live TV.  It would have to be a resolved by an assault, which the Yemenis are not trained to do.

"The Yemeni central government is very weak, it doesn't control its own territory," said Bergen, author of The Bin Laden I Know: An Oral History of Al Qaeda's Leader, among other works. 

Its population is, per capita, one of the most well-armed in the world.  It's mountainous territory, in the Arabian peninsula, a perfect place for AQ to thrive, as we have seen with a string of terror attacks that goes back to 1992.

The USS Cole was bombed there on Oct. 17, 2000, exactly eight years ago next month. 

Despite some officials' upbeat views on al Qaeda before today's attack, other top top military and State Department officials were warning  last May that the terrorists were changing tactics and looking for new avenues of attack.

They were right.

With Al Qa'ida in the Arabian Peninsula having sustained substantial losses in Saudi Arabia in recent years, it is natural that AQ militants would fall back on Yemen, where there is substantial ungoverned space, and a national government which has shown itself all too willing to negotiate with extremists.  Indeed, this past May, Abu Humam al-Qahtani, a Saudi member of AQ who has sought refuge in Yemen, issued a public invitation to the 'Saudi brothers, to avoid further losses by establishing a safe haven in Yemen.  The following month, Saudi officials effected several hundred more arrests.  

"I fully expect that the remnants of the Saudi AQ structure, as well as Saudi militants displaced from Iraq, will consolidate and launch future attacks from Yemen," said Grenier, now head of Global Security Consulting at Kroll.