Throughout Yemen's political crisis, the West's chief concern has been that spreading chaos in the country will offer al Qaeda in the Arabian Peninsula (AQAP) an opportunity to expand its operations. Now that Yemen's president, Ali Abdullah Saleh, is in Saudi Arabia for emergency medical treatment, leaving the country in uncertain hands, these worries have only become more urgent. Saleh has often argued that any political vacuum that would follow his rule could prove dangerously hospitable to al Qaeda and similar groups -- a warning that, in reality, is based far more on political posturing than on a real assessment of the terrorist threat.

For years now, Saleh has used the specter of al Qaeda to drum up political and financial support, mainly from the United States and Saudi Arabia. This strategy first took shape in November 2005, when he traveled to Washington to meet then U.S. President George W. Bush. Saleh expected his American hosts to congratulate him for eradicating the al Qaeda cells responsible for attacks on the U.S.S. Cole and the M.V. Limburg; instead, he was castigated for failing to achieve political and economic reforms. As he saw it, the danger of al Qaeda was the sole reason behind U.S. support for Yemen.

Three months later, the terrorist threat in Yemen took on new life when 23 experienced jihadis escaped from a high-security prison in Sana'a. A number of attacks on high-profile targets followed, mostly against Western tourists -- international oil workers in Marib and Hadhramaut in September 2006 and Spanish tourists at Marib in July 2007. Western diplomats were also targeted, most notably those at the U.S. Embassy, which came under a complex assault in September 2008. The attackers clearly wanted to damage Yemen's reputation and reduce tourism and oil revenues. Saleh, however, also stood to benefit from al Qaeda's rise: his less assertive response to terrorism than previously -- compared to, for example, his crackdown against those responsible for the Cole bombing -- may have been intended to raise the profile of jihadi groups in Yemen, and thus attract funding and training from the West for additional counterterrorist units to be controlled by members of his family.

In practice, the regular Yemeni army has performed most counterterrorist operations, and these special units have largely been deployed against domestic political opponents: the Zaydi revivalist Houthis in the north, who rebelled against governmental corruption and state sponsorship of Salafism; militants linked to the Joint Meeting Parties, the country's opposition coalition; and now the leaders of Hashid, Yemen's most powerful tribal confederation, who have come under attack after criticising Saleh for backing out of a deal to transfer power. Over the years, the Saleh regime has labelled each of these groups as terrorists in order to justify using forces that the state plainly regards as a sort of Praetorian Guard. In reality, the regime apparently feels far more threatened by domestic political enemies than by al Qaeda.

Not that Yemen isn't home to genuine terrorists. Al Qaeda in the Arabian Peninsula came into being in January 2009, when al Qaeda in Yemen merged with the remnants of al Qaeda in Saudi Arabia, which had been disrupted by Saudi security operations. At the same time, Anwar al-Awlaki, a Yemeni-American Islamist cleric and propagandist, began to work with AQAP. Since January 2009, AQAP has assassinated scores of Yemeni security officials, mounted a sophisticated two-phase attack on South Korean targets (first attacking a tourist party at Seiyun in March 2009, then attacking the investigative team in Sana'a three days later), dispatched the now infamous "underwear bomber" Umar Farouk Abdulmutallab, and attempted to blow up commercial airliners with bombs hidden in computer printers. It has also targeted the neighbouring Saudi regime: in an August 2009 suicide attack, an AQAP terrorist injured* Saudi Arabia's Deputy Minister of the Interior, Prince Muhammad bin Nayef, and in October 2009 two more would-be suicide bombers were killed trying to cross the Yemeni-Saudi border. (Their exact targets are unknown -- probably Saudi royals -- but they had two additional suicide vests, suggesting a major operation.) And then, as a sign of its increasing savviness, AQAP launched a slick online publication called Inspire, aimed at aspiring jihadis around the globe, particularly in the West.

But this catalogue of putative successes masks a number of fundamental vulnerabilities. It remains unclear how many members AQAP actually has -- perhaps a few hundred -- because incidents are often attributed to it inaccurately. For example, the Abida tribe near Marib, an area in Yemen's east rich in oil and natural gas, became enraged after a U.S. drone strike killed a senior sheikh in May 2010, possibly due to Saleh's duplicity. In response, the tribe has severed the main road in the area, interrupted power supplies to Sana'a, and blocked oil exports -- strikes that the Saleh regime regularly blames on al Qaeda. (In truth, the similarity of tactics often makes it difficult to determine whether tribesmen or jihadis are responsible for a particular attack.)

Similarly, the Islamists who recently established a so-called Islamic Emirate in the southern province of Abyan have denied that they are affiliated with al Qaeda, although they confess to having a common Islamist philosophy. Indeed, they have patrolled Jaar, one of Abyan's major towns, in tanks captured from the Yemeni army -- hardly the actions of al Qaeda militants living under the constant threat of missile attacks from U.S. drones. Yet the Saleh government has consistently labelled these Islamist insurgents as al Qaeda members ever since they took de facto control of Abyan. (They have, however, since been repulsed from their footing in Abyan's capital, Zinjibar.)

Saleh and a number of Western analysts have argued that many of the country's tribes provide sanctuary to AQAP members, making uncooperative tribal leaders and Islamist militants equal targets. Yet Yemen's tribes function as statelets, entirely capable of repudiating members who transgress tribal law or who represent a greater risk than providing sanctuary is worth. Indeed, over the last couple of years, Yemen's tribes have arranged several handovers of AQAP members to state security forces. The tribes have also created special tribal counterterrorism militias (on the model of the Iraqi al-Sahwa), although their effectiveness is debatable. What is clear is that the tribes are more than capable of neutralizing any al Qaeda presence in their homelands. The fact that they have not vanquished al Qaeda to date is less a testament to AQAP's strength or to tribal military weakness (after all, the al-Hashid tribal confederation is currently battling elements of the Yemeni military on equal footing) than to the fact that the tribes use AQAP as a bargaining chip with the government -- for example, to demand employment in special counterterrorist militias, which, of course, would not exist without the danger of terrorists.

Yemen's tribes and AQAP have far more potential points of friction than they do common cause. For starters, many of Yemen's combative tribes are Zaydis, a pragmatic Shiite sect, for whom the fundamentalist Sunni members of al Qaeda have a vitriolic ideological aversion. Beyond that, the jihadis threaten entrenched tribal interests, such as the production and use of qat (a mildly stimulant leaf beloved by many Yemenis but abhorrent to Salafis) and the lucrative trade of smuggling drugs and alcohol into Saudi Arabia.

Although AQAP describes itself as one organization, in practice the group is split in two: the domestic Yemeni group and those terrorists who fled Saudi Arabia. The two wings operate in separate areas using different methods. Indeed, their different tactics, and particularly their different weapons, suggest that they have little contact with each other. The more nationally focused faction of AQAP, based in the Abyan-Shabwa-Marib area, is of little threat to the West. Its cause is largely directed against the Saleh regime, meaning that with the demise of Saleh and his system of patronage, much of its raison d'être will end; where it does not, the tribes will drive it out since it will have outlived its usefulness.

The special operations group of AQAP, mostly constituted of transnational jihadis, remains a danger -- although more so to Saudi Arabia than to the West, for reasons of geography. Nevertheless, Saleh's political demise is likely to lead to the reform of the Yemeni state's many overlapping security organizations; this, in turn, will lead to the end of much of the unofficial cooperation between AQAP and sympathizers in the state security apparatus on which AQAP has depended to plan and mount its operations, such as the follow-up attack against the South Koreans. As a consequence, AQAP will find it far harder to achieve its attacks. From AQAP's limited use of suicide bombers to date, it would appear that AQAP does not have access to a large cadre of volunteers; similarly, the group's relatively slow pace of attacks suggests that it does not have many competent bomb-makers. Clearly, if Ibrahim al-Asiri, AQAP's master bomb-maker, can be removed from the picture, much of the special operations group's capability will be lost.

Of course, Western policymakers must consider the worst-case scenario: Yemen as a failed state. Pirates based in Somalia are already the scourge of the Gulf of Aden; additional bases for piracy on Yemen's southern coast would pose only a marginally increased threat. More important, Somalia is a haven for some transnational jihadis, but a poor operating base: there are few flights into or out of Somalia, and a limited number of attractive terrorist targets in the region. Yemen might descend into Somalia-style chaos, but the difficulties of sustaining the organization in such an environment would complicate AQAP's operation rather than enable it.

Even with Saleh gone, vested interests in an unreformed regime in Sana'a will ensure that al Qaeda continues to haunt the West and Saudi Arabia. Truly making Yemen inhospitable to al Qaeda would require a transition to parliamentary democracy, with security forces and other organs of the state answerable to institutions, not individuals. The increased transparency would limit corruption and reduce the opportunity for exclusive patronage networks -- and, with it, lower the resentment of those excluded that only fuels support for violence in Yemen.

* A previous version of this article said Prince Muhammad bin Nayef was killed by a suicide bomber; in fact, he was injured but survived the attack.