A year ago, Kenyan forces seized al-Shabab's final stronghold, the Somali port of Kismayo, sending the group into the country's rural interior and cutting off their economic lifeline. A long and brutal war against a slippery enemy, it seemed, was nearly won. After entering Somalia's conflict in October 2011, the Kenyan military, working together with the Somali National Army and the Ethiopian Defense Forces, had successfully weakened the Islamist terrorist group and seemed poised to restore peace to a fractured nation riddled by two decades of conflict. Those gains, it turns out, were fleeting. The three countries' militaries have been unable to wrestle control of Somalia's southern hinterlands from al-Shabab's forces. Provided an operational safe haven, but lacking a city base, al-Shabab transitioned from conventional fighting to asymmetric warfare using guerilla and terror attacks to target the new Somali Federal Government (SFG) in Mogadishu and now, tragically, in the heart of Kenya. Al-Shabab's brazen Sept. 21 attack on the luxury Westgate Mall in Nairobi, where an unknown number of its members killed at least 68 people and wounded 175, was just the latest step in its evolution from leader of an Islamic state in Somalia to a regional Islamist terror movement spreading its tentacles throughout the Horn of Africa. It's been barely 48 hours since the attack begin -- and as of this writing, the standoff continues -- but al-Shabab's motives seem clear: a vicious and bloodthirsty strike at the soft, civilian underbelly of East Africa's most important city to provoke a heavy-handed response, one that channels the popular support of disenfranchised Muslims in Kenya and re-energizes a terror group thought to be on the wane. Regardless of the motive, it's not yet possible to assess whether this attack signals the rebirth of al-Shabab as a regional jihadi movement, or the last gasp of a dying organization. Like any good guerrilla force, al-Shabab knows it has to conserve its sparse resources for maximum impact. Occurring less than a month before the second anniversary of Kenya's Somalia intervention, the attack comes during a nadir in relations between Nairobi and the SFG, which controls just a small swath of land in and around Mogadishu. Many in the Somali government are wondering when the Kenyan military will exit Kismayo, and doubt its intentions. The persistent theory in Mogadishu is that Kenya seems reluctant to turn over the valuable port, preferring to relinquish control to a warlord of its choosing rather than Somalia's central government. Meanwhile, many Kenyans are wondering when their troops will return home. For its part, al-Shabab may be hoping that the Westgate attack will convince Kenyans that a sustained involvement in Somalia is just too messy. And yet, it may also be a ploy to provoke Kenya, encouraging even greater commitment to sustaining forces in Somalia. On Twitter, al-Shabab called the attack "retributive justice for crimes committed" by Kenya's military, and witness accounts say that the terrorists reportedly targeted non-Muslims in the Westgate massacre. If the attack provokes Kenya to venture deeper into Somalia, al-Shabab hopes it can exhaust foreign forces in an asymmetric campaign of hide-and-seek insurgency. Inciting Kenya's rage and prompting an extended invasion is almost as positive an outcome for al-Shabab as getting the Kenyan military to unilaterally withdraw. Either way, the goal is the same: it's largely a matter of sequencing. The Westgate raid may also be intended to fan the flames of xenophobia. Resentment and persecution are familiar feelings to Somalis living in Kenya -- and for native Kenyan Muslims, as well, who have historically maintained a contentious relationship with the central government. It's too early to say whether Westgate will provoke retaliatory attacks against these communities in Kenya: much depends on whether or not the Kenyan government and security forces are willing and able to prevent an upwelling of violence against minority Muslims. Adding to the uncertainty, it's still unknown whether the majority of the attackers were Somali, or Somalis who had long resided in Kenya, Kenyans recruited to Somalia, or possibly Western foreign fighters dispatched from southern Somalia. If the attackers were residing in or native to Kenya, this would suggest a more sizeable base of popular support for al-Shabab in Kenya and potentially indicate the start of a broader campaign -- one likely met by a swift and brutal crackdown from Kenyan police and security forces. But that's not to say that this action has the backing of local elements. Previously, Somali diaspora communities -- like the one in Kenya -- had provided al-Shabab with crucial support. Clans aligned with al-Shabab leveraged their family networks, securing remittances to sustain their operations and attracting young Somali youth from as far away as Minneapolis to fill their ranks through online propaganda lauding the glory of combat. But the last two years have been tough for al-Shabab. In February 2011, the group's emir, Sheikh Moktar Ali Zubeyr (a.k.a. Ahmad Godane) arranged a merger with al Qaeda to shore up his power amongst al-Shabab's fractious clans. His ascendance coincided with a dramatic uptick in indiscriminant violence alienating al-Shabab's local popular support and creating rifts among its leaders. Up until 2011, al-Shabab -- more than any other al Qaeda affiliate -- had successfully attracted Westerners to fight in its ranks. However, under Godane's reign, foreign fighters were shunned in deference to indigenous Somali fighters more loyal to the emir. Instead of further empowering the organization, the merger created dissension among Shabab's clannish leaders: many felt that joining al Qaeda's global vision undermined their credibility amongst Somali clans wary of foreign influences. Likewise, Godane's killing of innocent Somalis began to create backlash and defection. Omar Hammami, the most well-known U.S. member of al-Shabab (and a popular inspiration in jihadi media) published a YouTube video fearing for his life -- and speaking about low morale and Godane's straying from sharia law. Hammami's video became the first of many public signs of a fracturing al-Shabab. Over the past 12 months, several key al-Shabab leaders have defected; Godane has gone after both Somali citizens and foreign fighters. And just this past week, reports emerged that al-Shabab murdered Hammami. It's a stretch to say that al-Shabab is reeling, but it's likely ostracized by the al Qaeda core for its very public internal disputes and factionalized by public dissension in the ranks. Needing to distract from killing one of its most celebrated members, a successful and public attack on Nairobi's Westgate Mall resets the agenda and helps Godane silence his critics. But while it seems strong and dangerous now, the health of al-Shabab is difficult to discern. In July 2010, the group claimed credit for a suicide bombing in Uganda that killed at least 74 people. "We are sending a message to Uganda and Burundi," the group's spokesperson said at the time, adding that if the two countries didn't withdraw their troops from Somalia, "blasts will continue." But follow up attacks never manifested. On Saturday, as the full nature of the Westgate raid became clear, al-Shabab on Twitter claimed this was the first of many attacks to come. If it quickly executes other attacks in Kenya, this would suggest a profound resurgence. If it fails to generate another attack over the next six months, the Westgate attack may represent a last desperate attempt to generate popular support, resources, and personnel. In terrorism, as in life, it's all about the follow through.