While it has long been believed that it was oil that added greatly to Daesh's clout, a recent trove of documents obtained by journalists casts doubt on the caveat.

The New York Times has managed to obtain thousands of files which the newspaper said "reveal the inner workings of a complex system of government" inside Daesh.*

The newspaper stressed that Daesh terrorists "did not rule by the sword alone," citing "brutality and bureaucracy," which it said added significantly to the group's clout.

READ MORE: US Helped Daesh in Attempt to Gain Control Over Syria's Oil — Damascus

The terrorists wielded power through a system of punitive taxes and fines for so-called immorality, such as eyebrow plucking, having the wrong haircut, playing cards, listening to music and smoking hookah pipes – an offense that could land a person in prison.

© AP Photo / Militant website Daesh terrorists pass by a convoy in Tel Abyad, northeast Syria (File)

"More surprisingly, the documents provide further evidence that the tax revenue the Islamic State earned far outstripped its income from oil sales. It was daily commerce and agriculture — not petroleum — that powered the economy of the caliphate," according to the New York Times.

In late 2017, an Iraqi military parade to celebrate the final defeat of Daesh was held in Baghdad's Green Zone, with December 10 being declared as an annual national holiday by the country's Prime Minister Haider al-Abadi.

READ MORE: Daesh Terrorists Earn Cash Through Online Casinos, Russian UN Envoy Says

Earlier that year, the Syrian Army declared victory over Daesh, citing the liberation of last town in Syria from the jihadists and the end of their three-year reign in the region.

This week, Russian President Vladimir Putin warned that even though Daesh had been defeated in Syria, the terrorist group's destructive potential is still in place.

READ MORE: Daesh Terrorists Planted Explosives in Nearly Every Building in Downtown Raqqa

"It is evident that despite its military situation, this terrorist group retains a significant destructive potential, and the ability to change its tactics quickly and attack countries and regions around the world," Putin pointed out.

Daesh announced the creation of a caliphate in 2014, in what was followed by the jihadists quickly seizing large swaths of territory in Iraq and Syria.

Three years later, the Russian-Syrian efforts added substantially to Daesh losing more than 90 percent of its territorial gains in Syria and Iraq, as well as its strongholds in Deir ez-Zor, Mosul and Raqqa.

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*Daesh (ISIL/ISIS/Islamic State), a terrorist group banned in Russia