- Abu Sayyaf was killed in a May, 2015 raid by US Special Forces in Syria
- Documents seized in the raid gave more intelligence than 'any Special Forces operation in history,' a State Department official has said
- Recent review of documents revealed how Abu Sayyaf ran ISIS oil fields
- He was known as fearsome boss who oversaw cash-only fuel trade
- In oil field salary negotiations, slave ownership was taken into account
- Picture shows Abu Sayyaf counting huge stacks of cash from oil sales
- Even after US destroyed 30% of ISIS oil infrastructure, daily sales still amount $1 million, documents reveal
Documents seized in the raid that killed a top ISIS oil executive last year have revealed details on how the terror group ran its $1million-a-day oil operation.
Paperwork reviewed by the Wall Street Journal shows ISIS oil man Abu Sayyaf had a job not unlike other oil executives - except he was also faced with issues like factoring slave ownership into salary negotiations, and repairing oil wells damaged in U.S. airstrikes.
A U.S. State Department official has said that more information was obtained from the documents seized in the raid against Abu Sayyaf than from 'any Special Forces operation in history.'
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An undated picture seized in the raid against Abu Sayyaf's Syrian compound in May 2015 shows the ISIS oil executive counting large stacks of cash. Documents reveal ISIS's oil operation is largely cash-based
Left, a file photo shows Syrian petroleum being drilled from wells in Kurdish-controlled Rimelan district. Right, ISIS fighters march in Raqqa, the terror group's main stronghold in Syria
Spreadsheets retrieved in the raid showed ISIS's total natural resource revenues in the six months that ended in February 2015 amounted to $289.5 million - and Abu Sayyaf's operation in the Deir Ezzour and al-Hasakah provinces in north-eastern Syria contributed to 72 percent of those revenues, the Journal reported.
Abu Sayyaf, a Tunisian who had his headquarters in the al-Omar field in Deir Ezzour, was known as a fearsome boss, who would threaten to relocate workers to oil fields in Iraq, where bosses were thought to be even worse, said Ibrahim, a 36-year old former oil worker interviewed by the Journal.
But other means of intimidation were much more sinister, Ibrahim said:
'You go to work and you find someone beheaded.'
Abu Sayyaf was killed on May 16, 2015 in a nighttime raid against his compund in north-east Syria
Abu Sayyaf, who was given custody in September 2014 of the American aid worker Kayla Mueller after she suffered as ISIS leader Abu Bakr al-Baghdadi's sex slave, was killed on May 16, 2015 in the nighttime raid against his compound in Deir Ezzour.
Under the direction of ISIS, Abu Sayyaf set up a system where private buyers would line up with trucks at oil fields, pay in cash for crude oil, and transport it in their own trucks, according to the Journal.
As the Daily Beast reported in December, the truckers would then sell the crude oil at a profit to local, makeshift refineries. There, fuel was produced to be sold at roadside pumping stations or in bulk to other smugglers, who go on to sell it in more populated areas.
U.S. aid worker Kayla Mueller was briefly held by Abu Sayyaf prior to her death in February 2015
In the end, the 'greater amount' of ISIS-produced oil was purchased by Syrian president Bashar al-Assad's regime, according to the U.S. Treasury Department.
'[Assad's regime and ISIS] are trying to slaughter each other and they are still engaged in millions and millions of dollars of trade,' said Adam Szubin, acting under secretary for Terrorism and Financial Intelligence with the Treasury Department, Reuters reported in December.
Some of the ISIS-produced oil also ended up in Turkey, the Treasury Department claimed.
The large profits ISIS made from oil prompted the U.S. to heavily target the group's oil infrastructure in its air raids. The campaign successfully dented ISIS's oil profits, making it less profitable today than taxation, the Journal reported.
However, even after U.S. air strikes destroyed 30 percent of ISIS's oil infrastructure, the terror group still makes about $1 million every day from selling oil, and the corporate structures set up under Abu Sayyaf remain intact, according to the Journal.
The terror group maintains its oil operation in part by offering handsome salaries to skilled oil workers: more than three times an average Syrian salary - $50 per month - for an accountant, and about eight times an average salary for a drilling technician.
It also factors in how many slaves and dependents a worker has when deciding salaries, the Journal reported.
According to the Journal, some of Abu Sayyaf's duties were taken over in March by the French jihadist Abu Mohammad al-Fransi, who reports to his predecessor's boss, Haji Hamid.