The tremors rumbling through the Arab world in the wake of the overthrow of Tunisia's long-entrenched president reached Yemen this weekend, as thousands of demonstrators on the campus of the University of San`aa called for the ouster of Yemeni President `Ali Abdullah Salih, calls which were echoed by southern pro-secessionists in the port city of Aden. This latest development adds to the package of difficulties faced by a central government which has never held either a monopoly on the means of coercion orbroad-based legitimacy, essential tools for a functioning modern state. One vitally important element in Yemen's woes in recent years has been al-Qa`ida.
Last October, Yemen became the focus of international attention when two explosive devices, sent from Yemen and intended for U.S. targets, were discovered on cargo planes in the UK and Dubai. The devices were linked to al-Qa`ida in the Arabian Peninsula (AQAP), which seems to confirm fears that Yemen is becoming a haven for militant organizations, with the potential for becoming a second Afghanistan.
Following the September 11, 2001 attacks, the international community began to view states such as Yemen not only as the sites of acute humanitarian distress but also as "failed states" that pose a threat to regional and international stability. Yemen, one of the less developed states in the Middle East, has suffered from ongoing instability for decades due to tribal wars, arms smuggling, and autonomous enclaves to which the law of the state does not extend. The attack on the USS Cole in October 2000 in the port of Aden constituted the inaugural declaration of al-Qa`ida's presence in Yemen. Since then, the group's activities have brought Yemen into the international limelight, especially in view of Yemen's increased geo-strategic importance, astride the Red Sea and just across from the Horn of Africa, and adjacent to Saudi Arabia, the greatest oil exporter in the world.
An estimated 16.3 percent of Yemenis are unemployed, and the birthrate is one of the highest in the world: the population is expected to double by 2040.  The World Bank's tough conditions for extending assistance have not helped the situation. On top of its economic woes, several new threats to the San`aa-based regime have emerged: a Shi`i rebellion in the north and a non-violent secessionist movement in the south, both of which resist San`aa’s political and economic domination. It is into this unstable scene thatal-Qa`ida has arrived, expanding its activities particularly in the south.
Al-Qa`ida has long considered Yemen, the homeland of the Bin Laden family, an attractive area due to its proximity to the Bab al-Mandab Straits, a highly important, geo-strategic maritime route. In AQAP's publication Sada al-Malahim (Echo of Battles), the organization's leaders argue that the demographic composition of Yemen and its mountainous topography turn it into a natural fortress that could provide shelter for jihadists. Nasir al-Wahayshi, the Emir ofal-Qa`ida in Yemen and therefore the leader of AQAP, considers al-Qa`ida's presence in Yemen part of its mission, enabling the organization to promote Islam from its birthplace in the Arabian peninsula. Al-Qa`ida's shift to Yemen could be considered a "return home."
A relatively large number of Yemeni civilians fought in al-Qa`ida'sranks, especially in Iraq, Afghanistan, and Pakistan. But the heavy hand used by the U.S. and its allies against al-Qa`ida activists created the need for a new shelter. Many al-Qa`ida members made their way to Yemen after having fought against the Americans in different parts of the region. However, these veterans are just one component in the widening base of support for al-Qa`ida's network in Yemen. The country’s poverty and tribal and religious conservatism make it a promising area for al-Qa`ida to carry out a long-term, systematic policy of ideological mobilization of the young people who constitute the majority of Yemen's rapidly growing population.
The San`aa regime’s weakness and the resultant power vacuum in several regions further add to Yemen’s potential for al-Qa`ida. San`aa's inability to exert its authority in portions of its sovereign territory has resulted in the creation of enclaves run by tribal militias, some of whom have made alliances with al-Qa`ida. These tribal groups view cooperation with al-Qa`ida as a means to better their lot and standing in Yemen. Such a pattern of shifting alliances can be found in abundance in Yemen's history. Tribes and other groups would side with a certain player not because of ideological motives, but in accordance with their evaluation of the local power game. A case in point is Marib, a region approximately one hundred and seventy kilometers east of San`aa, whose tribal groups’ relationship with the central authorities is characterized by friction. Marib and its adjacent provinces, Jawf and Shabwa, have become operational bases for al-Qa`ida activity. Fahd al-Quso, one of the most prominent Yemeni commanders in AQAP, is sheltered by the Awlak tribe in Shabwa.Al-Quso, who was thought to be in Pakistan, was quoted as saying that his presence in Yemen "is better" than in Pakistan "in light of the crisis situation with the Yemeni government."
Al-Qa`ida considers the San`aa regime corrupt and oppressive, allegations which give legitimacy to its operations in Yemen: the organization claims to be liberating the people. Additionally,al-Qa`ida spokesmen suggest that the San`aa regime has become a "Zionist- American tool" because it logistically supports the American presence on the Red Sea coast. The spokesmen also claim that President Salih supports U.S. actions in Somalia, a neighboring state in which U.S. forces periodically pursue al-Qa`ida operatives and other jihadists.
The San`aa regime, for its part, seems to be more concerned with southern secessionists and Shi`i rebels, which pose an immediate threat, than with AQAP. In its fight against the Shi`i Houthis, the government has even cooperated with radical Sunnis who may have ties to AQAP.  Much like the tribal leaders who change sides for political advantage, the San`aa government regards these alliances as fluid and temporary, necessary to achieve short-term goals. The U.S., however, is concerned that in so doing, San`aa is enabling al-Qa`ida and creating a long-term problem. John O. Brennan, chief counterterrorism adviser to President Obama, has said thatal-Qa`ida’s level of activity in the Yemen-Somalia zone is its highest anywhere.
Al-Qa`ida's presence in Yemen validates the argument that Yemen is becoming the next failed state. Like Afghanistan and Pakistan, Yemen and Somalia have become another regional focus in the global "war on terror." This is not to say that Yemen has reached the point of no return. But while the state's apparatus is being eroded and the government's influence is restricted to the urban areas, a broad swath of territory has become attractive and available for al-Qa`ida's activities.
Uzi Rabi is the is the Director of the Moshe Dayan Center and Chair of the Department of Middle Eastern and African History at Tel Aviv University.
 World Bank Group, Country Brief, Middle East and North Africa Region (MENA) – Yemen, September 2008.
 Tareq al-Humayd, "al-Yaman . . . Shukran lil-Qa`ida!" as-Sharq al-Awsat, 14 May 2009.
 Mark N. Katz, “Yemen and the ‘War on Terror,’” Middle East Policy Council, 11 January 2011