The ISIS earns around $2 million per day from the illicit sales of crude oil [representational image].Reuters

On the face of things, the ISIS (Islamic State of Iraq and Syria) seems like just another terrorist organisation. However, in reality, they are a "well-oiled" machinery - literally.

It is not a mere coincidence that the ISIS has grown from being a mere faction of the al-Qaeda to become one of the largest militant organisations in the Middle East. Back in its al-Qaeda days, the ISIS mostly relied up on large donations from its patrons to fund its operations.

However, it now seems to have become a completely self-funded organisation, raking in millions of dollars through bank robberies, kidnap ransoms, racketeering, selling ancient artefacts in the black market, taxes imposed on their subjects, and the most important of them all - the sale of crude oil. Through these operations, the ISIS has successfully converted itself into a wholly self-sufficient organisation, amassing a gross wealth of around $2 billion.

This wealth is not just a figure that would be eaten into, by the continuation of their operations. Reports suggest that the ISIS is here to stay (at least financially). They have created a revenue structure, through which they can keep on producing this amount of revenue through these subsidiary operations, in order to fund their primary operations, i.e expanding the Caliphate.

It is not a coincidence that the ISIS has around 80,000 men fighting for them at this moment. While some of these men have been forced to join the group, most have joined the ISIS of their own accord.

"July saw the largest recruitment since the group appeared in Syria in 2013, with more than 6,000 new fighters," said Rami Abdel Rahman, Director of the Syrian Observatory for Human Rights UK, speaking to Al Jazeera, last month. "The number of IS fighters has passed 50,000 in Syria, including 20,000 non-Syrians."

Records show that a couple of years ago, the ISIS had only around 1,000 men fighting for their cause. But these last two years has seen tens of thousands of men joining the militia. So what has caused such a huge rise in numbers?

"You get paid the most, you have the most weapons, you are with the most powerful group," said Jamal, an Iraqi Sunni, to BuzzFeed. "I'm not a fighter, but if I was that is who I'd join."

A resident of Tabqa city touring the streets on a motorcycle waves an Islamist flag in celebration after Islamic State militants took over Tabqa air base, in nearby Raqqa city.Reuters

Yes, among the armies in the Middle East, the ISIS pays their soldiers the best amount - $400 every month. In fact, this amount is almost double of what the other groups pay their fighters. It is much more than what the militant group of Hezbollah or the Free Syrian Army or even the Iraqi Army pay their soldiers.

The ISIS is not just another jihadist faction, operating with a poorly equipped army. They, in fact, have a very well planned out strategy on how to go about things, and have even set themselves annual objectives. They even publish an annual report, and function much like a multinational conglomerate.

According to experts, the ISIS have intricately studied other terrorist organisations of the past, like the FARC (Revolutionary Armed Forces of Columbia), who used to kidnap rich people for ransoms; the al-Qaeda, who levied taxes on the locals; and the Boko Haram, who made use of the natural resources under their rule, in order to fund their operations.

The ISIS has implemented these revenue-generating operations in such a manner that they are no more dependent on any external influence, for running their "Islamic State".

At the forefront of these revenue-generating operations lie the oil refineries. The ISIS controls six out of the 10 oil fields that are currently in operation in Syria, while they also control seven oil fields and two oil refineries in the northern parts of Iraq.

Experts from Iraq believe that the Iraqi fields under the control of the ISIS can produce up to 80,000 barrels of oil everyday. However, they claim the ISIS is currently producing only half that amount.

They also believe that the ISIS is selling crude oil in the black market for a considerably lesser price than others. The current price of a barrel of crude oil, in the black market, is said to be somewhere between $25 and $60. The ISIS is believed to be selling their barrels somewhere near the lower half of that price range. This means that they are earning somewhere around $2 million per day, from their Iraqi oil fields alone.

The amount that they earn from their Syrian oil fields is not quite clear because of the lack of proper statistical information. However, it is believed that they earn somewhere around the region of $3 million per day, just from the sale of crude oil, from both their Syrian and Iraqi oil fields.

This is an ingenious strategy as most of their enemies in the Middle East also depend on oil, and are compelled to buy the oil produced by the ISIS. They do not buy oil from the ISIS directly, however, as oil in the black market is mostly supplied to the refineries by the middlemen.

Most of the oil produced in the Syrian fields of ISIS ends up being sold to Bashar al-Assad's regime, against whom the former is fighting. Assad's regime needs the oil to survive, and cannot help but buy it. However, by buying it, the Syrians are funding their own demise.

It was only recently that buyers from Kurdistan found out that the oil that was making its way to them originated from the ISIS fields, and that their own money was being used to fund military operations against them.

Smoke rises during what activists said was an air raid by forces of Syria's President Bashar Al-Assad around al-Tabqa military base at a government-controlled airport that is surrounded by militants, west of Raqqa city.Reuters

Similarly, Turkey and Jordan have been trying to find the original source of the oil that ends up in their refineries. They do not buy the oil, if they find out that it originated from an ISIS field. However, some ISIS oil barrels do make their way into their refineries. They cannot help it because these barrels cannot be traced as they come through quite a few middlemen.

Experts believe that the next logical step for the ISIS will be to bring as many oil refineries as possible under their control. This way, they could effectively cut out the middlemen, and produce refined oil. This refined oil could be sold at a rate that is much cheaper that the rates offered by the competitors of the ISIS, creating a natural monopoly for the latter.

The ISIS are looking to build their organisation on a strong economic model, which not just looks at short term benefits but also at a sustainable future for the group. Everything they have done has been branded as acts of terrorism by the international community. However, if one takes a closer look, they have actually followed a proper model of growth, compared to other militant outfits, and chalked out every step they need to take.

Yes, their acts are terrible, affecting several innocent lives. But unlike other terrorist organisations, the ISIS have been following a proper economic model. By doing this, they have now become the richest militant organisation in the world.