Fifteen years after 9/11, confronting terrorism remains a central American priority. U.S. forces are still deployed in Afghanistan and Iraq; others carry out counterterrorism missions throughout the world. In recent years, opinions about al-Qaida's fortunes have sharply polarized. Many analysts and politicians were quick to write the organization's obituary after the killing of Osama bin Laden and the rise of jihadist challengers, such as the Islamic State, while others pointed to the continuing resilience of a long-established and still-potent organization.

As my book "The al-Qaeda Franchise" illustrates, the 9/11 attacks were a remarkable operational success for al-Qaida, but also a strategic challenge. In the past 15 years, the group has been forced to change how it organizes and operates by franchising local al-Qaida branches across borders, from North Africa to the Indian subcontinent.

Bin Laden targeted the American homeland as a means to transform the Middle East. He believed that by provoking the United States, al-Qaida would trigger a process ending in the elimination of American influence in Muslim countries, liberation of Muslim lands under foreign occupation, toppling of insufficiently Islamic regimes and the implementation of al-Qaida's radical version of Islamic law in Muslim countries. The United States may have lost some of its influence over Middle Eastern countries in recent years, and some of the rulers whom al-Qaida despised have indeed lost power, but the group's role in these developments was marginal.

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Al-Qaida succeeded in provoking an American response, but it quickly became evident that it lacked a viable plan to attain its objectives. al-Qaida believed that success requires mobilizing the Muslim masses, but those masses largely opposed the 9/11 attacks and the killing of innocent civilians. Only a few felt inspired to head to Afghanistan to resist the American assault that bin Laden had provoked.

Al-Qaida also lacked a plan for shifting its focus from terrorist attacks in the West to operating in the Middle East - the heart of its political agenda. Most Islamist groups based in the region denounced the attack instead of embracing al-Qaida. Some were also angry that al-Qaida dragged them into a U.S.-led conflict they did not want and for which they were totally unprepared.

Al-Qaida found itself isolated and fighting for survival in Pakistan's tribal areas. When U.S. forces invaded Iraq - seemingly confirming its narrative about American hostility to Muslims and Islam and providing a jihad arena in the heart of the Middle East - it had no meaningful presence there.

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The war in Iraq gave al-Qaida room to breathe. The group took advantage - and reinvented itself. Improvisation led leaders to adopt the franchise model, starting with Saudi Arabia and Iraq - and expanding throughout the Middle East. Through the creation of formal branches, al-Qaida was able to project an image of success despite meager operational capabilities and an inability to follow 9/11 with new large-scale attacks on American soil.

But this strategy came at a cost: It blurred the line between al-Qaida's distinct ideology of transnational jihad and that of national jihadist groups. It often put al-Qaida's fate in the hands of affiliates it could not control, and that tarnished its brand name.

Al-Qaida's relationship with Abu Musab al-Zarqawi was particularly harmful. The rogue jihadist's extremism, manifested in indiscriminate killing of Shiites and attempts to impose his branch on Iraq's Sunni groups, was a public-relations disaster for al-Qaida in Iraq and beyond.

A few years later, this branch would evolve into Islamic State fighters, directly challenging al-Qaida. Al-Qaida learned from that experience and was more careful not to rush into dangerous relationships in following years. Naturally, some expansions proved to be mixed successes or worse. But overall, al-Qaida became more cautious - evident by its keeping secret its organizational connections to Jabhat al-Nusra in Syria for two years.

Al-Qaida's expansion strategy helped the group retain its unique status within the jihadist movement. But as the memory of its 9/11 "success" faded, al-Qaida had less and less to show its constituency and financial supporters. Leaders tried, unpersuasively, to take credit for the global economic crisis of 2008, which they portrayed as a delayed consequence of the 2001 attack on the American homeland, and later for the Arab uprisings. Franchises kept the brand name alive but could not reverse the organization's rot.

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The open conflict with the Islamic State further exposed al-Qaida's difficulties maintaining its image as the leader of the global jihadist movement. The organization lost its edge to savvier actors - standing for even more extreme positions. By capturing vast territory and declaring its caliphate, the Islamic State demonstrated it could deliver on its agenda and promises, even as al-Qaida was issuing pronouncements.

But al-Qaida is hardly a spent force. The group has demonstrated remarkable resilience in the face of the Islamic State's challenge, retaining all its formal affiliates despite the rival organization's determined efforts to persuade them to defect and cripple them if they refuse. The disintegration of Middle East states after the Arab uprisings offered al-Qaida an unprecedented opportunity for a second start. The breakdown of order throughout the region allowed al-Qaida to get closer to Muslim communities, defend them and provide services -demonstrating that it can cooperate with other actors.

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These efforts are the culmination of a process that preceded the Arab uprisings. Learning from its mistakes, al-Qaida tried to expand its appeal beyond the community of jihadist sympathizers to a wider constituency of Sunni Muslims. Leader Ayman al-Zawahiri publicly instructed branches to refrain from carrying out attacks that might kill innocent Muslims. al-Qaida has also swiftly apologized for incidents of excesses from within its ranks and denounced operations that resulted in mass civilian casualties, even when carried out by its allies.

Al-Qaida has also changed how it interacts with civilian populations: In Yemen, Syria and Mali, the group labored to garner public support by providing services and not imposing harsh Islamic punishments. Unlike the Islamic State's brutal imposition of its version of sharia law, al-Qaida has taken a softer approach - though still fundamentally extreme -that emphasizes proselytizing and education. And al-Qaida has nurtured its image as the protector of Syria's Sunni population at a time when the world appears oblivious to their suffering.

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On the face of it, al-Qaida has a distinct transnational ideology that could appeal to many Muslims seeking common identity beyond their own states' borders. The group's assertions that it aspires to establish the coveted caliphate - but prioritizes fighting the Muslim nation's enemies first - resonate better with ordinary Muslims than does the Islamic State's worldview. In a way, the rival organization's genocidal approach has helped al-Qaida rebrand itself as a moderate jihadist actor.

But the power of local identities is still much stronger among jihadist sympathizers, and it is leading to the prioritization of franchises' local struggles at the expense of al-Qaida's U.S.-focused mission. Despite its expansion, al-Qaida's role has been reduced to providing guidance to its branches and planning operations outside the Middle East.

Jabhat al-Nusra's recent split from al-Qaida underscores these developments and the group's limitations. al-Qaida's ideology remains far too extreme for most Muslims, making it hard to deepen alliances with other Sunni groups, and its continuing rejection by the international community frustrated its Syrian affiliate's efforts to reap the benefits of its battleground success. Thus, even after it proved its worth for the Syrian opposition, capitalizing on its success required Jabhat al-Nusra to declare its independence.

In a way, the 9/11 attacks that propelled al-Qaida to the top of the global jihadist movement are now hindering its ability to become a strong political force, preventing it from taking full advantage of the turmoil in the Middle East. Fifteen years later, the threat al-Qaida poses to the United States has diminished considerably even as jihadist groups are flourishing throughout the Middle East. The group might be able to reinvent itself once again, but with its anti-American agenda looking increasingly irrelevant, it will have to settle for a much more limited role as the elders of the jihadist movement, restricted to advisory missions and propaganda.