Peter Bergen is CNN's national security analyst, a vice president at New America and a professor of practice at Arizona State University. He is the author of " United States of Jihad: Investigating America's Homegrown Terrorists ."

Baghdad, Iraq (CNN) Lt. Gen. Abdul-Wahab al-Saadi is virtually unknown outside Iraq, but he is a hero in his own country. When the three-star general walks into the lobby of a guesthouse in Baghdad he is quickly surrounded by well-wishers who want to take selfies with him. Iraqis know that the taciturn general was key to the long, grinding campaign that defeated ISIS.

Last week the Iraqi military released a statement saying Iraq was "fully liberated" from ISIS' reign of terror. Three years earlier, ISIS had controlled 40% of the country, according to Iraqi officials.

It was the storied "Golden Division" of Iraq's Counter-Terrorism Service, the Iraqi version of US Special Operations Forces, that did much of the fighting and dying to defeat ISIS.

Saadi leads the Golden Division. A tall, thin man with deep, dark circles under his eyes that are a testament to his fight against ISIS for the past three years, Saadi, 54, was dressed in a black leather jacket, black shirt and black trousers when he sat down to discuss the campaign against ISIS over a cup of tea in Baghdad.

Saadi asserted that all that remains of ISIS in Iraq are "some sleeper cells." Surviving ISIS cells have gone to ground in western Iraq, Syria and Turkey, he said.

Two months ago President Donald Trump was quick to take credit for the looming defeat of ISIS when Raqqa, ISIS' de facto capital in Syria, fell to US-backed forces. Trump asserted that ISIS hadn't been defeated earlier because "you didn't have Trump as your president."

Saadi seemed genuinely puzzled when asked if he had noticed any changes in American support during the more than two years that he had been leading the Iraqi fight against ISIS. Saadi said, "There was no difference between the support given by Obama and Trump."

Why is it that the US-trained Golden Division and Counter-Terrorism Service played such a key role in the defeat of ISIS while the Iraqi army ignominiously fled from the ISIS militants that seized much of Iraq in 2014?

Saadi explained, "We have zero tolerance for sectarianism," which has been the bane of Iraqi security services. Iraq's minority Sunni population have long viewed the Iraqi security services as armed Shia groups with a deeply sectarian agenda.

The Counter-Terrorism Service, consisting of about 10,000 soldiers, also demands continuous training for its soldiers, unlike the Iraqi army, which only requires basic training.

The prestige of the Counter-Terrorism Service can be gauged by the fact that when the Iraqi government launched a recruitment drive in May, 300,000 men applied to be part of the force. An American military trainer said that only around 1,000 of those will likely end up being trained at a joint US-Iraqi training facility, according to a report in the Washington Post.

Saadi said American logistical and intelligence support and US airpower accounted for "50% of the success of the battle" against ISIS. American bombs inflicted heavy casualties on ISIS and were a morale booster for Saadi's troops.

Saadi led the Golden Division into battle in key phases of the war against ISIS, liberating first Iraq's key oil refineries in Baiji in June 2015, and then significant Iraqi cities such as Fallujah, Ramadi and Tikrit.

When he was fighting to liberate Tikrit the general tore off the three stars on his epaulettes denoting his high rank, he told me, saying to himself, "I don't deserve this rank if I don't free my fellow citizens from the grasp of ISIS."

The general leads from the front. "I have to be in the front line. Number one it is for the morale of my soldiers, and second I want to make sure no one mistreats civilians," Saadi said. As a result, the general has narrowly escaped death repeatedly, showing this reporter a scar on his chin where he says a sniper's bullet grazed him during the battle of Baiji.

It was above all his role in the fight for Iraq's second city, Mosul, that cemented Saadi's reputation among Iraqis.

The fight for Mosul was never going to be easy. A city of 2 million people, the old section of the city in western Mosul is a warren of narrow medieval-era streets and buildings.

The battle for Mosul lasted nine months -- in part, Saadi said, because Iraqi forces didn't want to level the city: "We were very careful to preserve the infrastructure and also the lives of innocents remaining in the city."

The fight was also complicated in Mosul because ISIS deployed more than 1,000 "VBIEDs" --vehicle-borne improvised explosive devices -- cars and trucks driven by suicide bombers. These VBIEDs were greatly feared by the Golden Division troops.

Also many of ISIS' most competent fighters, numbering around 10,000, decided to make their last stand in Mosul where ISIS' self-styled caliphate was first proclaimed in 2014 by Abu Bakr al-Baghdadi, the elusive leader of ISIS.

Mosul finally fell to Iraqi forces in July.

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Reflecting on the anti-ISIS campaign, Ben Connable, a political scientist at the RAND think tank, who served in Iraq for three tours as a Marine Corps officer said, "I have never been more optimistic about Iraq than I am today. They finally feel like they own their security."

The battle against ISIS in Iraq is over. The next challenge for the Iraqi government is to win the peace. To do that, it must now ensure that Iraq's Sunni minority feels that they have some real stake in Iraqi politics so that they don't actively or passively support groups like ISIS that claim -- no matter how self-servingly -- to stand up for the rights of the Sunni.