TWO WARS are underway that simultaneously target Islamic State (ISIS) terrorists in Iraq and Syria. One involves fighters, warplanes and bombs. The other is the Green War. Green, as in money.

Both wars are on full display this week. In Syria, American and Arab warplanes pounded oil refineries controlled by ISIS terrorists. In Washington, the U.S. slapped economic sanctions on 11 people and one nongovernmental organization that it said were sending financial and other support to terrorist groups, including ISIS.

The Green War hinges on a single time-proven principle: An army marches on its stomach. Bleed ISIS of its funding, and you cripple its ability to recruit, train, supply and dispatch jihadists across Iraq and Syria.

One reason ISIS has grown so fast and been so successful in luring jihadists from around the globe is that it pays well — an estimated $600 a month to fighters.

How can ISIS afford it? Its seizure of vast chunks of Iraq and Syria has yielded a huge windfall: The group earns up to $2 million a day in oil revenues from a dozen or so major oil fields and refineries in the area that it controls.

Bombing oil fields needn't be the Green War's only theater of battle.

President Obama has proudly reeled off the list of Arab nations joining this U.S.-led coalition, but our Arab allies can do far more to defeat ISIS than send warplanes. They can help choke off the flow of cash to the jihadists. They can put the squeeze on ISIS's private donors in their respective countries. They can make it clear to businessmen that dealing with ISIS petroleum brokers on the black market will bring them a world of financial pain.

Many European countries, also slow to join the coalition, ought to play vital roles. Some of those countries reportedly have paid ransoms to jihadists for the return of their citizens. The world has to stop funding terrorism-by-ransom-demand, as gut-wrenching as it is to refuse when an innocent person's life is at stake.

In some cases, economic sanctions are among the most formidable and fearsome weapons in the Western arsenal. Ask Iran and Russia. But ISIS isn't an established state with strong connections to the international banking system. It appears to be largely circumventing that system to raise funds via the illicit oil sales, kidnappings and other acts of extortion.

But some of the group's money inevitably must find its way into banks. Bankers may think they can look the other way. This week, a federal jury in Brooklyn delivered a powerful message: No, you can't. The jury found Arab Bank, a major Middle Eastern bank, liable for providing support to the terrorist organization Hamas.

The jury said that even if the bank was following international rules, it should have known it was handling transactions for terrorists, even if the terrorists' names did not appear on certain blacklists. One juror who spoke to reporters after the verdict got it right. Money, she said, is "oxygen for the terrorists."

The Green War is one important way to cut off that oxygen. The Daily News occasionally runs editorials from other sources. This first appeared in the Chicago Tribune.