(CNN) "You will conquer Rome and own the world," ISIS leader Abu Bakr al-Baghdadi told his followers in July 2014.

In the previous month, a few hundred ISIS fighters had seized Mosul, Iraq's second-largest city, in a matter of hours. They drove thousands of Iraqi troops from the city, in the process getting their hands on a huge arsenal of US-supplied weaponry Iraqi forces had left behind. They went on to conquer a string of towns and cities, reaching the outskirts of Baghdad.

At its height, Baghdadi's so-called caliphate r eigned over a realm the size of Britain, with 10 million people under its sway. Its sudden catapult to world attention, combined with an uncanny mastery at social media and slick video production, attracted thousands of people from around the globe eager to take part in the new utopian experiment.

Now, four and a half years later, that realm has all but disappeared, after Kurdish forces said Saturday that they captured the eastern Syrian pocket of Baghouz, the last populated area under ISIS rule.

Kurdish-led Syrian Democratic Forces have launched multiple operations since early February to bring the caliphate to an end. Night and day, artillery and mortar barrages and warplanes from the US-led foreign coalition pounded ISIS' final encampment: a sprawling junkyard of wrecked cars and tattered tents.

Tens of thousands of people have left ISIS' last stronghold since the barrage began, including ISIS jihadis who have surrendered.

In an ISIS video, people could be seen running for cover while others fired from the barricades. In its final week, the shell-cratered pocket held as many as 5,000 people and defied all predictions of a swift and final defeat.

The group still has some fighters in central Syria and has gone underground in Iraq, where it continues to stage surprise attacks.

An image grab taken from a video released on July 5, 2014 by Al-Furqan Media shows alleged ISIS leader Abu Bakr al-Baghdadi preaching during Friday prayer at a mosque in Mosul.

ISIS as a territorial entity, a quasi-state, is history. The scars left by ISIS, and the long war against it, will take decades to heal.

In June 2015, I visited a school in Baghdad that had been turned into a temporary home for people who had experienced life in Mosul under ISIS and had fled the madness.

One of them, Louay Shawkat, was an Iraqi army veteran, now confined to a wheelchair.

He told me he had fought the Iranians in Iraq's eight-year war with that country, fought the Americans in 1991. ISIS, he said, is different.

"It's an illness," he said. "It's impossible to cure. Cancer can be cured. Tuberculosis can be cured. Almost every illness can be cured, but not this one."

Indeed, we've seen the cancer manifest. In the perverse, lurid video beheadings of American journalist James Foley and other journalists; in the burning, alive in a cage, of Jordanian air force pilot Moath al-Kasasbeh. The Jordanian's murder was shot from multiple angles, the entire production edited together by someone who was clearly a professional. Countless murders captured on camera in the most gruesome detail were spread across the globe by social media.

Photo of Jordanian pilot Moath al-Kasasbeh in uniform. Video and still images surfaced on Feb. 3, 2015, showing the pilot being burned alive while confined in a cage.

We saw it in the mass murder and enslavement of Yazidis in Iraq and Syria, where ISIS killed the old and infirm and the able-bodied men, and sold the women and children into slavery. ISIS didn't conceal, didn't deny and didn't cover up any of it.

While many of the regimes in the Middle East try to hide their barbarity, will go to great lengths to conceal their violations of human rights, will spend tens of millions of dollars on lobbying and public relations firms to conceal the true nature of their rule, ISIS boasted of its brutality, took pride in its savagery.

In 2015, I went to Baharka refugee camp outside Erbil, in northern Iraq. There I met Ibrahim, a Palestinian born in Haifa. He fled his home in 1948 at the age of 11, eventually ending up in Mosul, where he experienced life under ISIS first hand.

"The things we've seen were enough to drive you mad," he recounted, sitting cross-legged on a blanket in his family's tent.

"We ran away," his son, Tamer, interjected. "I didn't want my children to see any more horrible things. In Mosul, we'd drive down the street and see dogs eating dead bodies in the road."

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Like the Yazidis, Christians who found themselves in the path of ISIS's onslaught knew that as non-Muslims their fate was bleak at best.

Father Gabriel Touma was born in the northern Iraqi Christian town of Al-Qosh and lived there all his life. When I met him in early 2015, he recalled that, just months before, ISIS forces were just six kilometers, less than four miles, from the town.

"I stood before the statue of the Virgin Mary and wept with a broken heart," he told me. "I prayed to her to protect us from evil."

He had seen what ISIS had done in nearby Mosul, where they toppled crosses off church roofs, vandalizing their contents, sequestered property owned by Christians and imposed taxes on those who refused to convert.

"It's like knife stabbing us in the heart, when we see our heritage, our history, the work of our forefathers, being destroyed before our eyes and we're helpless to do anything to stop it," he said. "It's a slow death."

Photos: Mosul: Iraqi-led forces push into key city Members of the Iraqi federal police wave the country's flag as they celebrate in the Old City of Mosul on July 9, 2017. Iraq declared victory against ISIS forces in Mosul after a grueling monthslong campaign. The battle to reclaim Mosul, the last major ISIS stronghold in Iraq, has been underway since fall 2016. Hide Caption 1 of 73 Photos: Mosul: Iraqi-led forces push into key city This injured girl was found by Iraqi forces as they advanced against ISIS militants in the Old City of Mosul on Monday, July 3. She was carried away for medical assistance. Hide Caption 2 of 73 Photos: Mosul: Iraqi-led forces push into key city A suspected ISIS fighter is held in a basement while Iraqi forces continue to push for control of the Old City of Mosul on Monday, July 3. Hide Caption 3 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi Special Forces soldier exchanges fire with ISIS militants in the Old City on Friday, June 30. Hide Caption 4 of 73 Photos: Mosul: Iraqi-led forces push into key city A bomb explodes near the al-Nuri mosque complex on Thursday, June 29. Iraq's military has seized the remains of the Great Mosque of al-Nuri. Iraq and the United States have accused ISIS of blowing up the historic mosque. Hide Caption 5 of 73 Photos: Mosul: Iraqi-led forces push into key city Members of the Iraqi Federal Police hold a position as US-led coalition forces advance through the Old City on Wednesday, June 28. Hide Caption 6 of 73 Photos: Mosul: Iraqi-led forces push into key city The remnants of Mosul's ancient leaning minaret are seen in the Old City on Sunday, June 25. ISIS' claim that US warplanes were responsible for the destruction of the minaret is "1,000% false," US officials told CNN. Hide Caption 7 of 73 Photos: Mosul: Iraqi-led forces push into key city Two boys comfort each other after their home collapsed during fighting between Iraqi forces and militants in Mosul on Saturday, June 24. The boys, who are cousins, said some of their relatives were still under the rubble. Hide Caption 8 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi soldier helps transport a girl as residents flee their homes west of Mosul on Friday, May 26. Hide Caption 9 of 73 Photos: Mosul: Iraqi-led forces push into key city Displaced Iraqis make their way through rubble after evacuating their homes in a neighborhood of west Mosul on Wednesday, May 17. Hide Caption 10 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi man tries to extinguish a burning car during fighting in Mosul's western Rifai neighborhood on Tuesday, May 16. Hide Caption 11 of 73 Photos: Mosul: Iraqi-led forces push into key city A member of the Iraqi counterterrorism service secures a building as troops push toward Mosul's Al-Oraibi western district on Sunday, May 14. Hide Caption 12 of 73 Photos: Mosul: Iraqi-led forces push into key city A smoke cloud rises on the front line as the Iraqi Emergency Response Division advances in west Mosul on Saturday, May 6. Hide Caption 13 of 73 Photos: Mosul: Iraqi-led forces push into key city A wounded man is transported in western Mosul on Friday, April 21. Hide Caption 14 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi federal policeman smokes during a break from battle on Wednesday, April 12. Hide Caption 15 of 73 Photos: Mosul: Iraqi-led forces push into key city A member of Iraq's security forces stands guard in eastern Mosul as smoke rises from the ISIS-controlled western section of the city on Friday, April 7. Hide Caption 16 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqis visit a bath house on the southern outskirts of Mosul on Wednesday, April 5. Hide Caption 17 of 73 Photos: Mosul: Iraqi-led forces push into key city Flames billow from an explosion in Mosul during a clash between Iraqi forces and ISIS fighters on Sunday, March 5. Hide Caption 18 of 73 Photos: Mosul: Iraqi-led forces push into key city Families are forced to evacuate as Iraqi forces advance in western Mosul on Thursday, March 2. The number of internally displaced people has surged as the offensive effort has intensified. Hide Caption 19 of 73 Photos: Mosul: Iraqi-led forces push into key city Mosul residents cross a damaged bridge in the al-Sukkar neighborhood on Saturday, January 21. Hide Caption 20 of 73 Photos: Mosul: Iraqi-led forces push into key city French President Francois Hollande and French Defense Minister Jean-Yves Le Drian, right, view territory held by ISIS during a visit to a military outpost near Mosul on Monday, January 2. Hide Caption 21 of 73 Photos: Mosul: Iraqi-led forces push into key city A young girl takes part in a Christmas Day Mass at a church in the predominantly Christian town of Qaraqosh. The area's churches were heavily damaged by ISIS militants before the town was freed by Iraqi forces during the Mosul offensive. Hide Caption 22 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi Shiite fighters ride through a desert area near the village of Al-Boutha al-Sharqiyah, west of Mosul, on Friday, December 2. Hide Caption 23 of 73 Photos: Mosul: Iraqi-led forces push into key city Internally displaced Iraqis who fled the fighting in Mosul watch as a civilian drone films them at the al-Khazir camp on Thursday, December 1. Hide Caption 24 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi soldier searches a home for ISIS militants after Iraqi forces retook the village of Al-Qasr on Wednesday, November 30. Hide Caption 25 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi soldiers transport a comrade who was injured during a battle near the village of Haj Ali on Tuesday, November 29. Hide Caption 26 of 73 Photos: Mosul: Iraqi-led forces push into key city A man mourns during the funeral of four Iraqi paramilitary fighters who were killed in battles in the town of Tal Afar. Hide Caption 27 of 73 Photos: Mosul: Iraqi-led forces push into key city Displaced civilians return to the village of Tall Abtah on Friday, November 25, after Iraqi forces retook the village from ISIS. Hide Caption 28 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi civilians sit on the ground in Mosul on November 24. An Iraqi officer addressed the group, demanding to know the whereabouts of alleged ISIS militants who opened fire on troops a few days earlier. Hide Caption 29 of 73 Photos: Mosul: Iraqi-led forces push into key city An injured baby receives treatment at a field hospital in Mosul on November 15. Hide Caption 30 of 73 Photos: Mosul: Iraqi-led forces push into key city A woman cries Sunday, November 13, after seeing the St. Addai church that was damaged by ISIS fighters during their occupation of the Keramlis village. Hide Caption 31 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi special forces soldier prays next to a Humvee before troops pushed toward Mosul's Karkukli neighborhood on November 13. Hide Caption 32 of 73 Photos: Mosul: Iraqi-led forces push into key city A Kurdish Peshmerga fighter holds part of a defused bomb planted by ISIS militants in Bashiqa, Iraq, on Friday, November 11. Hide Caption 33 of 73 Photos: Mosul: Iraqi-led forces push into key city A member of Iraq's special forces guards two suspected ISIS fighters found hiding in a house in Mosul on November 11. Hide Caption 34 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi woman displaced by war holds her cat near a checkpoint in the Iraqi village of Shaqouli, east of Mosul, on November 10. Hide Caption 35 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi troops watch a broadcast of Donald Trump's acceptance speech in a house in Arbid, on the outskirts of Mosul, on Wednesday, November 9. Iraqi Prime Minister Haider al-Abadi congratulated Trump on his win and said he hoped for continued support in the war on ISIS. Hide Caption 36 of 73 Photos: Mosul: Iraqi-led forces push into key city US Marines install equipment at a coalition base in Qayyara on November 9. Hide Caption 37 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi forces member investigates a mass grave that was discovered after coalition forces recaptured the area of Hamam al-Alil on Monday, November 7. Hide Caption 38 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi children witness a man being interrogated by a member of the Iraqi army at a base next to the Al-Intissar neighborhood of Mosul on November 7. Hide Caption 39 of 73 Photos: Mosul: Iraqi-led forces push into key city A civilian man who fled the fighting trims his beard after reaching an Iraqi army position in Mosul on November 7. Hide Caption 40 of 73 Photos: Mosul: Iraqi-led forces push into key city Children play in debris created by an airstrike in Qayyara on Sunday, November 6. Hide Caption 41 of 73 Photos: Mosul: Iraqi-led forces push into key city Female members of the Freedom Party of Kurdistan sing as they hold a position near Bashiqa on November 6. Hide Caption 42 of 73 Photos: Mosul: Iraqi-led forces push into key city A baby is passed through a fence back to his mother at a refugee camp in the Khazir region on Saturday, November 5. Hide Caption 43 of 73 Photos: Mosul: Iraqi-led forces push into key city People line up to receive food at a refugee camp in the Khazir region on November 5. Thousands are taking refuge in camps set up for internally displaced people. Hide Caption 44 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi soldiers pass near a bridge destroyed in an airstrike in Qayyara on November 5. Hide Caption 45 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi soldiers patrol an alley on the outskirts of Mosul on Friday, November 4. Hide Caption 46 of 73 Photos: Mosul: Iraqi-led forces push into key city A suspected member of ISIS is detained at a checkpoint near Bartella, Iraq, on November 4. Hide Caption 47 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi families pack into a truck to be moved to camps on Thursday, November 3. Hide Caption 48 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi special forces soldier searches for the location of an ISIS sniper in Gogjali on November 1. Hide Caption 49 of 73 Photos: Mosul: Iraqi-led forces push into key city A man fleeing the village of Bazwaya carries a white flag as he arrives at a checkpoint on November 1. Hide Caption 50 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi soldier receives treatment after being injured during clashes with ISIS fighters near Bazwaya on October 31. Hide Caption 51 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi soldier navigates through a shattered windshield as coalition forces advance on Bazwaya on October 31. Hide Caption 52 of 73 Photos: Mosul: Iraqi-led forces push into key city Archbishop Yohanna Petros Mouche, center, performs Mass in the liberated town of Qaraqosh on Sunday, October 30. Hide Caption 53 of 73 Photos: Mosul: Iraqi-led forces push into key city Children play in a camp for internally displaced people near Kirkuk, Iraq, on October 30. More than 600 families from Tel Afar, a town west of Mosul, have been living in the camp since ISIS took control of the area in 2014. Hide Caption 54 of 73 Photos: Mosul: Iraqi-led forces push into key city Displaced families are seen on the road near Qayyara on Saturday, October 29. Hide Caption 55 of 73 Photos: Mosul: Iraqi-led forces push into key city U.S. military personnel take cover in a bunker after a mortar alarm was sounded at a coalition air base in Qayyara on Friday, October 28. Hide Caption 56 of 73 Photos: Mosul: Iraqi-led forces push into key city Women and children grieve over the grave of a family member at a Qayyara cemetery damaged by ISIS on October 27. Hide Caption 57 of 73 Photos: Mosul: Iraqi-led forces push into key city Residents of Qayyara wait for distribution of food and water rations on October 26. Local water sources have been contaminated by the burning oil and sulfur. Hide Caption 58 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraq's counterterrorism forces advance toward ISIS positions in Tob Zawa on October 25. Hide Caption 59 of 73 Photos: Mosul: Iraqi-led forces push into key city Soldiers give first aid to an injured boy in Tob Zawa on October 25. Hide Caption 60 of 73 Photos: Mosul: Iraqi-led forces push into key city Kurdish Peshmerga forces take positions as they start to move toward the Imam Reza and Tizxirab villages of the Bashiqa district on Sunday, October 23. Hide Caption 61 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi forces distribute fruit in the village of al-Khuwayn, south of Mosul, after recapturing it from ISIS on October 23. Hide Caption 62 of 73 Photos: Mosul: Iraqi-led forces push into key city Kurdish security forces detain a suspected member of ISIS in the eastern suburbs of Kirkuk on Saturday, October 22. Hide Caption 63 of 73 Photos: Mosul: Iraqi-led forces push into key city An Iraqi forces member helps a man push a car as they arrive at a refugee camp in Qayyara on October 22. Hide Caption 64 of 73 Photos: Mosul: Iraqi-led forces push into key city Spent bullet cartridges litter the street around the Jihad Hotel, where ISIS militants battled Iraqi security forces in Kirkuk on Friday, October 21. Hide Caption 65 of 73 Photos: Mosul: Iraqi-led forces push into key city Gen. Abdel Ghani al-Asadi, who leads Iraq's counterterrorism forces, sits in Bartella on October 21 after the town was reclaimed. Hide Caption 66 of 73 Photos: Mosul: Iraqi-led forces push into key city Peshmerga fighters look over a village during an assault near Bashiqa on Thursday, October 20. Hide Caption 67 of 73 Photos: Mosul: Iraqi-led forces push into key city Iraqi forces head toward the front lines near Qayyara on Tuesday, October 18. Hide Caption 68 of 73 Photos: Mosul: Iraqi-led forces push into key city A Peshmerga fighter peers up from an underground tunnel in the liberated town of Badana on October 18. ISIS fighters have built tunnels below residential streets to escape from airstrikes. Hide Caption 69 of 73 Photos: Mosul: Iraqi-led forces push into key city Kurdish security forces take up a position near ISIS-controlled villages on Monday, October 17. Hide Caption 70 of 73 Photos: Mosul: Iraqi-led forces push into key city Smoke rises from a suicide car bomb attack carried out by ISIS in the village of Bedene on October 17. Hide Caption 71 of 73 Photos: Mosul: Iraqi-led forces push into key city Members of the Iraqi coalition gather around a fire at Zardak mountain ahead of the offensive. Hide Caption 72 of 73 Photos: Mosul: Iraqi-led forces push into key city Peshmerga forces deploy in the dark near the village of Wardak early on October 17. Hide Caption 73 of 73

But ISIS's reign of terror didn't spare those who might have seen it in a more positive light.

Abdel Razaq Hamadi, a Sunni tribal leader in Al-Dour, a town outside Tikrit, Iraq, recounted to me that when ISIS took control, they attacked his home, killing his wife, two sons and two grandsons.

He was under no illusion about the group, regardless of their claims to piety, and took up arms against ISIS.

"I know the people who killed my family," he said. "We want to fight these terrorists, drive them out of this area and never see them again."

Two years later, on the outskirts of Mosul at the height of the offensive to retake the city, I sat with Mariam, a women in her 70s, by the side of the road. She was resting after fleeing her home, chain-smoking the cigarettes ISIS had forbidden her to have.

She had no illusions.

"They took pills. They drank alcohol. They oppressed us," she spat out scornfully. "But when they came to you, they'd say 'God says this, Muhammad says that.'"

In the town of Al-Alam, near Tikrit, we were there when trucks piled high with mattresses, household possessions and people drove into the town, bringing home residents after ISIS had fled.

"Thank God we're home," said a woman, who identified herself only as Um Nour, the mother of Nour. "We've been freed from ISIS. May God curse them until judgment day!"

Indeed, today much of Syria and Iraq has been freed from ISIS, but its curse lives on. There, the group has morphed into a low-level insurgency, carrying out hit-and-run attacks and bombings.

And beyond, in Libya, Egypt's Sinai Peninsula, Nigeria, the Philippines, Afghanistan and elsewhere, groups that have pledged allegiance to ISIS still control territory. And ISIS continues to inspire so-called lone wolves to carry out attacks.

Female fighters of the Syrian Democratic Forces (SDF) gather during a celebration at the Al-Naim square in Raqqa on October 19, 2017, after retaking the city from ISIS.

While some may be tempted to celebrate what is seen as ISIS's demise, the fertile soil in which ISIS grew and spread is still there.

Brutal regimes across the Middle East have emerged from the Arab Spring more adept than ever at repression. The prisons are full of the innocent and the guilty rounded up by police states adept in the art of torture and coercion. At the same time, a new wave of unrest, fueled by anger over the rising cost of living, is beginning to raise its head, spurred on by the inability of these very same states, teetering on the brink of failure due to incompetence, corruption, bankruptcy and brutality.

Unless all of that changes, ISIS or something perhaps even worse, like a demonic phoenix will rise again from the ashes of Abu Bakr al-Baghdadi's ruined realm.