A report released this week by the Department of Defense’s Inspector General indicates that ISIS continues to pose a significant threat in the Middle East.

“Despite losing its territorial ‘caliphate,’ the Islamic State in Iraq and Syria (ISIS) solidified its insurgent capabilities in Iraq and was resurging in Syria” from April through June, the report said.

During that time period, U.S. forces in Syria fulfilled the Trump administration’s directive to partly withdraw from the country. Military officials told the inspector general’s office that “the reduction of U.S. forces has decreased the support available for Syrian partner forces at a time when their foces [sic] need more training and equipping to respond to the ISIS resurgence,” Principal Deputy Inspector General Glenn A. Fine wrote in the opening of the report.

Military officials also said that ISIS is working to increase its power in Iraq, where the government declared victory over the group in December 2017.

The report drew in part on information provided by  the Combined Joint Task Force-Operation Inherent Resolve (CJTF-OIR), the military command that carries out the U.S.-led anti-ISIS effort and coordinates with coalition partners.

Officials told the inspector general’s office that ISIS continues to function as an insurgency in both Iraq and Syria partly because forces there “remain unable to sustain long-term operations against ISIS militants.” ISIS is also “likely reestablishing financial networks in both countries,” according to officials at the Office of the DoD Deputy Assistant Secretary for Counternarcotics and Global Threats.

Beyond that, military officials warned, ISIS “maintains an extensive worldwide social media effort to recruit fighters.”

How did the self-proclaimed Islamic State come to be in the first place? How has the battle against it — and the U.S.’s involvement — played out across the Middle East? And how has the group’s brutal strategy changed over the years? FRONTLINE has been covering ISIS’s bloody and complex evolution since its earliest days. Here are five documentaries that explore the ISIS threat.

Syria’s Second Front (February 2014)

Before the world was paying attention, FRONTLINE aired U.S. television’s first in-depth report on a troubling development in the Syrian conflict: the emergence of a brutal group known as ISIS. FRONTLINE correspondent Muhammad Ali found that three years in to Syria’s civil war, rebel forces were now fighting not just the Assad regime, but a dangerous group of jihadists that was starting to capture territory in the country. Ali, a Syrian native, snuck into a town that had been captured by ISIS and filmed with the rebel movement as it prepared to launch one of its first major attacks against the group. “Just like we fought Bashar, we fought ISIS. They’re even worse than the regime,” a young fighter named Hazem told him afterwards. In words that now ring tragic, he went on to say, “Once we finish with ISIS, we can return to fighting Assad and deliver a serious blow to the regime.”

Losing Iraq (July 2014)

In June of 2014, ISIS stunned the world by seizing Mosul, Iraq’s second-largest city, after taking control of wide swaths of territory in Syria. But as this film from Michael Kirk and his team explored, ISIS didn’t come out of nowhere: Its roots were laid in the aftermath of the U.S. invasion of Iraq. The film traces the U.S.’s role in the country from the 2003 invasion to the bloody emergence of a terror group that, as former U.S. Ambassador to Iraq Ryan Crocker told FRONTLINE, made “bin Laden’s al Qaeda look like Boy Scouts.”

The Rise of ISIS (October 2014)

Reporting from Iraq as U.S. airstrikes against ISIS began, Martin Smith examined the buildup of unheeded warnings, failures and missed opportunities that allowed Al Qaeda in Iraq to become ISIS. The film offers a revelatory look at how ISIS grew out of the disaffection of Iraqi Sunnis who were sidelined after the American withdrawal, how the group gained strength in Syria, and how it developed and funded its brutal strategy. “This is one of the first terrorist groups saying, ‘You know what? We’re not going to hit and run, and we’re never going to participate in politics as you know it. We actually want to kill everyone who disagrees with us,’” counterterrorism expert Ali Soufan told FRONTLINE.

The Secret History of ISIS (May 2016)

How was ISIS’s founder Abu Musab al-Zarqawi, once a small-time criminal, able to build a brutal terrorist organization that would destabilize the Middle East and inflict violence around the world? Michael Kirk’s film takes an in-depth look at how Zarqawi developed what would become the ISIS playbook — fomenting sectarian violence among Muslims, stepping in to take advantage of power vacuums, and broadcasting beheadings on the internet — right under the U.S. government’s nose. The film also explores how Zarqawi’s successor, Abu Bakr al Baghdadi, followed Zarqawi’s method to make ISIS an even more powerful threat.

Confronting ISIS (October 2016)

Martin Smith traveled to five countries with key roles in the anti-ISIS fight — Saudi Arabia, Iraq, Syria, Jordan and Turkey — to report on successes, failures and challenges as ISIS lost ground in the region, but lashed out with attacks abroad. He found that the conditions that helped give rise to ISIS in the first place, including sectarianism, were still prevailing in many cases — and that America and its allies in the fight against ISIS often had clashing agendas.

Explore FRONTLINE’s full archive of reporting on the ISIS threat here, and see our reporting on the conflicts in Syria and Iraq here.

Patrice Taddonio, Senior Digital Writer, FRONTLINE

Email:

patrice_taddonio@wgbh.org

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@ptaddonio