It was surprising and shocking news yesterday that Fort Hood murderer Maj. Nidal Malik Hasan prowled radical jihadist chatrooms in the year before his attack, and that his avowed and extreme views tripped no serious alarms whatsoever. But what should shock no one is that when he looked for inspiration, he found it here, in Yemen.

According to reports, in the months before his rampage Hasan sought counsel from Anwar al Awlaki, a former imam at the Dar al Hijra Mosque, where Hasan worshiped irregularly during his years in the Washington, D.C. area. Awlaki, a former Muslim chaplain at George Washington University, traded 10 to 20 friendly emails with Hasan, according to The New York Times. The imam—whose views the mosque's current leadership has publicly rejected—left the United States and fled to Britain and then Yemen, which is one of the world's most hospitable places for extremist Sunni thought.

Bad publicity surrounding Hasan’s mentor may rebound, to Saleh’s embarrassment. His troubles are already doubling: In addition to the Shiite revolt, a more diffuse separatist movement is gathering energy in the south, centered on Aden.

Awlaki spent two years in prison in Yemen, but was released without charge and now maintains a blog and enjoys an affiliation with Iman University, a Sanaa Islamic school run by accused terrorist Shaykh Abdul Majid al Zindani. Moreover, he operates in an environment where radical jihadist tendencies are actively encouraged, even by a government that styles itself a friend of the United States. Ramzi bin al Shibh, an al Qaeda terrorist to whom even Khalid Sheikh Muhammad deferred in matters of religion, hails from here, and al Qaeda chose it as the site of one of its first and most spectacular attacks, the bombing of the USS Cole at the port of Aden in 1999. Osama bin Laden's father, Muhammad bin Laden, grew up in the starkly beautiful Hadramaut region of Yemen, and Osama himself occasionally appeared in videos with Yemeni daggers, to symbolize his continued affinity for the country.

• Retired Army Col. Ken Allard: The Next Fort HoodYemen is one of several gathering points for Muslims looking for serious study of the Koran. Just yesterday, at the Ashairiyyah Mosque in the ancient city of Zabid, I briefly met with a small group from Indonesia and Malaysia who had come to study the Koran with local scholars. There was no indication that they or their teachers were inclined toward violence, but like many others they had come so far because Yemen has long been preeminent in its nurturing of Islam of a pure and conservative sort.

The Yemeni president, Ali Abdullah Saleh, has the support of the United States government, which correctly views him as the only national figure capable of being a strongman who can hold the fragile Yemeni state together and bind the Yemeni armed forces into a unit capable of cooperating on counterterrorism and anti-piracy. (Although Somalia gets all the heat and bad publicity for piracy—witness the taking of British holidaymakers Rachel and Paul Chandler last month—this helpful map shows that the Yemeni coast is equally in need of patrolling.)

And in the last few years, internal strife has led Saleh to make devil's bargains with America's worst enemies to keep his power secure. In the northern province of Sa'dah, members of a Shiite sect known as the Zaydis have mounted an armed challenge to his rule, and in the last few days that challenge has blossomed into full-scale civil war. To counter the Shia rebellion (known as Houthi, for its ex-leader Hussein Badr al Din al Houthi), Saleh has enlisted the cooperation of Sunni extremists, known to some as Wahhabis and to themselves as Salafis, such as Nidal Hasan's mentor al Zindani.

It is the same cynical pact critics have alleged the Saudis to have entered more than a decade earlier: befriending extreme Sunnis and encouraging them to turn their violence toward a shared external enemy, so that they do not act out against the state. The Salafis regard Shia as blasphemers, so in Saudi Arabia the Shia of the eastern provinces face discrimination for their faith, and Iran, the region's key Shiite state, is regarded with extreme suspicion. Similarly, Saleh has pumped up his country's own robust Salafi population, and has even claimed the Houthi revolt is sponsored by Iran—an unlikely possibility, since the Zaydi Shia split from the Iranian Twelver Shia roughly 1,300 years ago and have irreconcilable doctrinal differences.

Bad publicity surrounding Hasan's mentor may rebound, to Saleh's embarrassment. His troubles are already doubling: In addition to the Shiite revolt, a more diffuse separatist movement is gathering energy in the south, centered on Aden. It will, if it crescendoes into a war as hot as the one in the north, leave few avenues for Yemen to bind itself back together, even through another dangerous deal with its enemies.

Graeme Wood has been an Atlantic staff editor since 2006. His blog, Prepared for the Worst, chronicles a journey through Iraq, Afghanistan, the Arabian peninsula, and the Horn of Africa.