The extremist group that is threatening the existence of the Iraqi state was built and grown for years with the help of elite donors from American supposed allies in the Persian Gulf region. There, the threat of Iran, Assad, and the Sunni-Shiite sectarian war trumps the U.S. goal of stability and moderation in the region.

It’s an ironic twist, especially for donors in Kuwait (who, to be fair, back a wide variety of militias). ISIS has aligned itself with remnants of the Baathist regime once led by Saddam Hussein. Back in 1990, the U.S. attacked Iraq in order to liberate Kuwait from Hussein’s clutches. Now Kuwait is helping the rise of his successors.

As ISIS takes over town after town in Iraq, they are acquiring money and supplies including American made vehicles, arms, and ammunition. The group reportedly scored $430 million this week when they looted the main bank in Mosul. They reportedly now have a stream of steady income sources, including from selling oil in the Northern Syrian regions they control, sometimes directly to the Assad regime.

But in the years they were getting started, a key component of ISIS’s support came from wealthy individuals in the Arab Gulf States of Kuwait, Qatar and Saudi Arabia. Sometimes the support came with the tacit nod of approval from those regimes; often, it took advantage of poor money laundering protections in those states, according to officials, experts, and leaders of the Syrian opposition, which is fighting ISIS as well as the regime.

“Everybody knows the money is going through Kuwait and that it’s coming from the Arab Gulf,” said Andrew Tabler, senior fellow at the Washington Institute for Near East Policy. “Kuwait’s banking system and its money changers have long been a huge problem because they are a major conduit for money to extremist groups in Syria and now Iraq.”

Iraqi Prime Minister Nouri al-Maliki has been publicly accusing Saudi Arabia and Qatar of funding ISIS for months. Several reports have detailed how private Gulf funding to various Syrian rebel groups has splintered the Syrian opposition and paved the way for the rise of groups like ISIS and others.

Gulf donors support ISIS, the Syrian branch of al Qaeda called the al Nusrah Front, and other Islamic groups fighting on the ground in Syria because they feel an obligation to protect Sunnis suffering under the atrocities of the Assad regime. Many of these backers don’t trust or like the American backed moderate opposition, which the West has refused to provide significant arms to.

Under significant U.S. pressure, the Arab Gulf governments have belatedly been cracking down on funding to Sunni extremist groups, but Gulf regimes are also under domestic pressure to fight in what many Sunnis see as an unavoidable Shiite-Sunni regional war that is only getting worse by the day.

“ISIS is part of the Sunni forces that are fighting Shia forces in this regional sectarian conflict. They are in an existential battle with both the (Iranian aligned) Maliki government and the Assad regime,” said Tabler. “The U.S. has made the case as strongly as they can to regional countries, including Kuwait. But ultimately when you take a hands off, leading from behind approach to things, people don’t take you seriously and they take matters into their own hands.”

Donors in Kuwait, the Sunni majority Kingdom on Iraq’s border, have taken advantage of Kuwait’s weak financial rules to channel hundreds of millions of dollars to a host of Syrian rebel brigades, according to a December 2013 report by The Brookings Institution, a Washington think tank that receives some funding from the Qatari government.

“Over the last two and a half years, Kuwait has emerged as a financing and organizational hub for charities and individuals supporting Syria’s myriad rebel groups,” the report said. “Today, there is evidence that Kuwaiti donors have backed rebels who have committed atrocities and who are either directly linked to al-Qa’ida or cooperate with its affiliated brigades on the ground.”

Kuwaiti donors collect funds from donors in other Arab Gulf countries and the money often travels through Turkey or Jordan before reaching its Syrian destination, the report said. The governments of Kuwait, Qatar, and Saudi Arabia have passed laws to curb the flow of illicit funds, but many donors still operate out in the open. The Brookings paper argues the U.S. government needs to do more.

“The U.S. Treasury is aware of this activity and has expressed concern about this flow of private financing. But Western diplomats’ and officials’ general response has been a collective shrug,” the report states.

When confronted with the problem, Gulf leaders often justify allowing their Salafi constituents to fund Syrian extremist groups by pointing back to what they see as a failed U.S. policy in Syria and a loss of credibility after President Obama reneged on his pledge to strike Assad after the regime used chemical weapons.

That’s what Prince Bandar bin Sultan, head of Saudi intelligence since 2012 and former Saudi ambassador in Washington, reportedly told Secretary of State John Kerry when Kerry pressed him on Saudi financing of extremist groups earlier this year. Saudi Arabia has retaken a leadership role in past months guiding help to the Syrian armed rebels, displacing Qatar, which was seen as supporting some of the worst of the worst organizations on the ground.

The rise of ISIS, a group that officially broke with al Qaeda core last year, is devastating for the moderate Syrian opposition, which is now fighting a war on two fronts, severely outmanned and outgunned by both extremist groups and the regime. There is increasing evidence that Assad is working with ISIS to squash the Free Syrian Army.

But the Syrian moderate opposition is also wary of confronting the Arab Gulf states about their support for extremist groups. The rebels are still competing for those governments’ favor and they are dependent on other types of support from Arab Gulf countries. So instead, they blame others—the regimes in Tehran and Damascus, for examples—for ISIS’ rise.

“The Iraqi State of Iraq and the [Sham] received support from Iran and the Syrian intelligence,” said Hassan Hachimi, Head of Political Affairs for the United States and Canada for Syrian National Coalition, at the Brookings U.S.-Islamic World Forum in Doha this week.

“There are private individuals in the Gulf that do support extremist groups there,” along with other funding sources, countered Mouaz Moustafa, executive director of the Syrian Emergency Task Force, a Syrian-American organization that supports the opposition “[The extremist groups] are the most well-resourced on the ground… If the United States and the international community better resourced [moderate] battalions… then many of the people will take that option instead of the other one.”