It has been a momentous month for the Islamic State of Iraq and the Levant (ISIL). The group was cast out of Al Qaeda, which criticized its ultra-aggressive strategy in Syria. Preceding the announcement, ISIL exerted its power in three countries. In Syria, its units clashed with rebels weary of the group’s unyielding campaign of murder and violence. In Lebanon, ISIL claimed credit for a suicide car bombing in a Hizballah stronghold. 450 miles to the east, in its most audacious effort, ISIL’s black-clad fighters stormed Ramadi and Fallujah, the two major cities of Iraq’s Anbar Province, and appeared to maintain control over Fallujah.

ISIL’s takeover of Fallujah is a homecoming for the group, which a decade ago set up shop in the city. There, a Jordanian terrorist with the nom de guerre Abu Musab al Zarqawi would devise a blood-soaked path to victory that promoted cyclical sectarian warfare rather than the phased, patient efforts promoted by most jihadist theorists. It was a cynical, audacious and chillingly effective blueprint which has expanded the reach of the global jihad faster and farther than Osama Bin Laden or Ayman al-Zawahiri, who ironically cautioned Zarqawi against pursuing such a radical path. Despite Zawahiri’s reticence, Zarqawi’s successors have fiercely advanced his design, roiling the politics of the Middle East and bringing the region closer to a catastrophic sectarian faceoff.

Little in Zarqawi’s background suggested he would come to shape the global jihad and events in the Middle East to such an extent. Zarqawi, then thirty-seven, spent much of his life in jail or on the margins of society, plying jihadist violence in Jordan and Afghanistan. Perhaps it was this street-level existence that allowed him to identify the Shi’ite threat that, properly manipulated, could motivate Sunnis to take up arms under the banner of Al Qaeda to an extent that the enemies of the classic Al Qaeda narrative—the far-off West and its allied governments—ever could. Writing in 2004, Zarqawi opined:

“The Shi'a in our opinion, these are the key to change. Targeting and striking their religious, political, and military symbols, will make them show their rage against the Sunnis and bear their inner vengeance. If we succeed in dragging them into a sectarian war, this will awaken the sleepy Sunnis who are fearful of destruction and death at the hands of these [Shi’a]...Fighting the Shi'a is the way to take the nation to battle…”

Over the next two years Zarqawi put his plan into action, overseeing a relentless campaign of mass casualty attacks against Shi’ite civilians and holy shrines that continues unabated. By the time of his death in August 2006, Zarqawi’s vision was largely realized: battles between Sunni insurgents and Shi’ite death squads ripped Iraq apart, leading a war-weary US public to agitate for withdrawal. However, Zarqawi’s plan and Al Qaeda in Iraq’s fortunes declined over the next few years, reaching such a nadir in 2010 that some observers declared the group dead. For a moment, it appeared Zarqawi’s murderous vision had died with its author.

To Western observers and even some jihadists themselves, AQI’s reversal suggested Zarqawi’s violent vision had little staying power and was vulnerable to countermeasures. Put simply, groups that embraced vicious and apparently self-defeating tactics could never attract public support and would eventually burn out. This is a comforting diagnosis, which is also very wrong. AQI declined from 2007 to 2011 because of a fortuitous combination of factors: the opposition of a powerful and sophisticated US military, which helped engineer a pause in sectarian violence, enabling the rise of an organized Sunni resistance movement (the Awakening).

Today, in Syria, Iraq, and increasingly Lebanon, it is hard to imagine such a combination of factors arising. Over the past three years Zarqawi’s successors doggedly adhered to his core guidance and engineered a remarkable revival, brutally expanding and exporting the sectarian blood-bath that helps sustain the group. ISIL’s ferocity and heavy-handed tactics, often labeled as missteps, are calculated attempts to attract new supporters and assert control over resources and rivals. Western observers may recoil from the group’s single-minded focus on violence and label it as reckless, but it is a strategy that has helped the group rebuild and pushed the Middle East to the brink. Zarqawi responded in 2004 to his critics:

“Some people will say, that this will be a reckless and irresponsible action that will bring the Islamic nation to a battle for which the Islamic nation is unprepared. Souls will perish and blood will be spilled. This is, however, exactly what we want.”

Zarqawi’s prescient embrace of the region’s darker sectarian impulses has helped cement ISIL’s presence to a degree unimaginable just a few years ago. The group’s direct involvement in the key battlefields of the global jihad, its simple and violent prescription to the supposed Shi’ite threat, and its identification with the sectarian currents which are dominating the conflicts in the Middle East increasingly grants it greater influence on the direction of the global jihad.

Some in the West may take a measure of comfort from the sectarian focus of ISIL, envisioning an intractable but local struggle between Sunni and Shi’ite fanatics that draws terrorist attentions away from the West. This is a false hope; ISIL’s sectarian focus should be thought of as a stepping stone, a means to an end, that end being the formation of an expansive extremist entity capable of targeting the main enemy: the West and Israel. Indeed, Zarqawi himself targeted Western interests throughout the Middle East, and viewed ISIL’s sectarian war as a bridge to grander, transnational efforts:

“When the Mujahidin would have secured a land they can use as a base to hit the Shi'a inside their own lands, with a directed media and a strategic action, there will be a continuation between the Mujahidin inside and outside of Iraq.”

As ISIL’s power and safe haven grows, his successors are likely to find the time and resources to lash out at the West. Addressing Americans last month, Zarqawi’s successor Abu Bakr al-Baghdadi stated "soon we will be in a direct confrontation and the sons of Islam have prepared for such a day. So watch for we are with you, watching." Given ISIL’s penchant for following through on its designs, it would be wise to take al-Baghdadi at his word.

Patrick Devenny is an analyst for the US Government. His views are his own.