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A worker walks up the stairs on the side of an oil tank at the Total refinery in Grandpuits, near Paris, January 6, 2015. Global oil markets slumped on Tuesday for a fourth straight day, still seeking a bottom with crude prices at their lowest since spring 2009 on mounting worries about a global supply glut. REUTERS/Christian Hartmann REUTERS/Christian Hartmann

Rear Adm. John Kirby, Pentagon Press Secretary, has alluded that oil has ceased to be the main income stream of the extremist militant group ISIS.

In a press briefing on Tuesday, Kirby said they noticed that the “lead source” of the ISIS’ income has been “changing.” Although he said the Pentagon has yet to fully ascertain the group’s dominant source of income nowadays, the spate of kidnappings and beheadings the ISIS recently displayed could be an indicator it’s relying on that strategy to replenish lost money in its coffers.

As with most oil-producing nations, the ISIS is also affected by the continued drop in the prices of the basic commodity in the world market. When it seized critical oil wells in Iraq, the ISIS was believed to have been capable of churning over 80,000 barrels a day of oil. It then sells these over at the black market for a discounted price. Overall, before the oil price drop, it was estimated the group earns as much as between $1 million to $3 million a day.

Then came the U.S.-led airstrikes which strategized to target refineries associated with oil production that the ISIS had captured earlier. The airstrikes, according to estimates by the International Energy Agency, disrupted the production of oil so much that the group now only controls about 20,000 barrels per day in the month of October alone, down from about 70,000 in August. The airstrikes, the IEA said, had “frustrated the jihadists’ ability to operate oil fields and refineries.” Michael Knights, an Iraq expert at the Washington Institute for Near East Policy, told Bloomberg in October that the group has gone from “the richest terrorist group in history to the world’s poorest nation-state.”

On Monday and Tuesday, Kirby said the US-led coalition carried out 14 airstrikes against the ISIS in Syria and Iraq, respectively. The coalition is composed of more than 60 nations, Jordan included.

On Tuesday, the ISIS released a video showing they burned Jordanian pilot Muath al-Kasaesbeh in a cage while still alive. Al-Kasaesbeh was captured in December when his plane crashed in northern Syria.

In retaliation, Jordan executed two al Qaeda prisoners before dawn Wednesday. They were Sajida al-Rishawi, the Iraqi failed suicide bomber whom the ISIS had previously requested to be released, as well as Ziad Karbouli, a former top aide to the deceased leader of al Qaeda in Iraq, Abu Musab al-Zarqawi.

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