Some of the most successful fighters against the Islamic State are being isolated and attacked by America’s new favorite ally in the region.

Kurdish militias are achieving the stated goals of the Obama administration — to “degrade and ultimately destroy” ISIS — as well or better than any other fighting force. From Kobane to the recent liberation of Tel Abyad, Kurdish militias have won hard-fought victories against ISIS fighters in Syria, while preventing the advance of ISIS into northern Iraq.

What’s more, the Kurds in northern Syria have established a political order like few others in this region of the world. Known as Rojava, the Kurdish-controlled areas of Syria are governed through participatory decision-making forums that include councils made up of women, Christians, Yazidis and Muslims. David Graeber, a leading figure in the Occupy Wall Street movement, calls Rojava a “remarkable democratic experiment.”

But those gains are now in danger as Turkey, which has a long history of enmity towards ethnic Kurds and fears the potential for a Kurdish state to its immediate south, in northern Syria or Iraq, flexes its political muscle in Washington and applies its military might in the Middle East.

Behind the scenes, American lobbyists employed by Turkey started working to block U.S. military assistance to Kurdish fighters last year, lobbying disclosures show.

This past week, the Turkish government made two critical air bases available to U.S. forces, a long-sought concession that allows the U.S. military to launch anti-ISIS raids more quickly. And it began its own airstrikes against ISIS. But that move is increasingly being seen as something of a feint, with Turkey’s main focus being a new offensive against Kurdish militants.

Simultaneously with its announcement about U.S. access to the air bases, the Turkish government broke its truce with Kurdish militants. During the past week, the Turkish military began attacking Kurdish bases in Iraq and allegedly in Syria as well. The Turkish government says its campaign is simply a response to an attack by the Kurdistan Worker’s Party (PKK), a separatist group, and has emphasized that it is also targeting ISIS.

On Friday, Turkey launched a series of mass arrests. Though some ISIS supporters were detained, the “vast majority” of arrests, according to the local press, were of leftists and Kurds. And on Tuesday, Turkey’s President Recep Tayyip Erdogan called for a crackdown on the People’s Democratic Party, a Kurdish-leftist political party that gained seats in parliament for the first time last month.

Turkey intends to use the increased airstrikes to create a “safe zone” for Sunni Arab militias, which as the New York Times noted, would come at the expense of Kurdish fighters.

Rather than condemn the attacks on the Kurds, the Obama administration praised Turkey’s government for making its air base available.

Turkey’s role as a coalition partner in the campaign against ISIS has been and remains the subject of some controversy. For years, foreign jihadi fighters trickled through Turkey’s porous border to join the ranks of ISIS. The Guardian reported on Saturday that a recent U.S.-led raid on an ISIS official responsible for selling black market oil to traders in Turkey revealed direct dealings between Turkish officials and ranking ISIS members

Vice President Joseph Biden remarked on this strange relationship with Turkey in a speech in October 2014. Turkey, Biden said, is “so determined to take down [Syrian President Bashar Assad’s government] and essentially have a proxy Sunni-Shia war, what did they do? They poured hundreds of millions of dollars and tens, thousands of tons of weapons into anyone who would fight against Assad — except that the people who were being supplied were al Nusra and al Qaeda and the extremist elements of jihadis coming from other parts of the world.”

Biden quickly apologized, as good an example as any of the pressure to maintain long-standing U.S.-Turkey business and military relationships — and the intractable power of the Turkish lobby, which is among the biggest spenders on foreign lobbying in Washington and a major sponsor of congressional junkets.

Turkey employs an all-star lobbying team of former government officials, including former Democratic lawmakers Dick Gephardt and Al Wynn; former Republican Senator Tim Hutchinson; retired Central Intelligence Agency Director Porter Goss; and, until he was indicted in June and left the Dickstein Shapiro law firm, former Speaker of the House Denny Hastert. Others on the payroll include Brian Forni, a former Democratic aide, the law firm Greenberg Traurig, and Goldin Solutions, a media strategy firm.

A number of public relations firms and lawyers help sponsor junkets to American politicians and journalists to visit Turkey. Turkish Coalition of America, a Turkish interest group that helps to sponsor the trips, retained Brown, Lloyd and James, the lobby group that, in an ironic twist, previously represented Assad’s wife.

Recently, the Turkish lobby has worked to block military support to the Kurds working to defeat ISIS.

The battle has been over legislation that would allow President Obama to bypass the Iraqi government in Baghdad and directly provide Iraqi Kurds with the heavy weapons and armored vehicles needed to battle ISIS. In the House, Reps. Ed Royce, R-Calif., and Elliot Engel, D-N.Y., the House Foreign Affairs Committee chairman and ranking member, introduced a bill last November, and then again in March, to provide the administration with the appropriate authority to arm the Kurds.

David Thompson, a former Capitol Hill staffer retained by the Turkish government, lobbied House Republican leaders on the Royce-Engel legislation in late 2014. The firm contacted aides to GOP leaders Kevin McCarthy and Steve Scalise regarding the bill, according to the statement filed by Thompson’s law firm, Dickstein Shapiro, with the Justice Department in January.

Turkish interests say they have legitimate concerns about the bill. “Supporting a militia for money and then unleashing them into the wild of terrorism we think is irresponsible,” said Gunay Evinch, a longtime attorney for the Turkish government and former president of the Assembly of Turkish American Associations.

“There are tidal wave kind of ripple effects that could be caused just by flooding a particular group within a broader group with heavy weapons and it could dwarf the ISIS problem or multiply it to many types of problems,” Evinch added. Evinch said that he was speaking only on behalf of the ATAA board of directors, not the Turkish government. He noted that he met with Turkish embassy officials, who said they had supplied information to congressional intelligence officials about the dangers of supplying Kurdish forces with weapons.

Human rights watchdogs point out that in some areas of Iraq, Kurdish forces have been linked with efforts to segregate Arab and Kurdish refugees.

Embassy officials and Thompson did not respond to multiple request for comment about the bill. The Turkish embassy later sent a fact-sheet claiming, “Though acting with different motivations, [ISIS] and the PKK share similar tactics and goals.”

President Erdogan has been clear about the threat posed by Kurdish militias. “I say to the international community that whatever price must be paid, we will never allow the establishment of a new state on our southern frontier in the north of Syria,” Erdogan said last month.

“Turkey has legitimate concerns about the international and American long-term policy towards Syria as well as in Iraq,” G. Lincoln McCurdy, the president of the Turkish Coalition of America, said in October. McCurdy, whose group organizes congressional junkets to Turkey and serves as the treasurer of a pro-Turkey political action committee, noted that he is working to improve Turkey’s image as a member of the anti-ISIS coalition, and stressed the need to highlight Turkey’s role as a major host country for refugees.

“We’re in a very strong position because of the PACs,” McCurdy explained to a gathering of Turkish American leaders and Turkish embassy officials in March. He pointed to the strong pro-Turkey sentiment of Rep. Brendan Boyle, D-Pa., a freshman lawmaker and a member of the House Foreign Affairs Committee.

At the event, Boyle took the stage, praising Turkey as “one of our best friends, if not the best friend, in the region.” He went on to chide his fellow lawmakers for introducing “nine anti-Turkish resolutions,” a reference to legislation to recognize the Armenian genocide and condemn Turkey’s efforts to restrict Internet freedom. “This is wrong and counterproductive and bad for U.S.-Turkish policy,” he declared. About a week after Boyle’s remarks, McCurdy’s Turkish Coalition PAC contributed $1,000 to Boyle’s reelection campaign.

When the Royce-Engel bill to arm Kurds against ISIS was reintroduced this year, most members of the House Foreign Affairs Committee signed on as co-sponsors. Boyle was not among them. Asked why he did not sign onto the legislation, Boyle’s spokesperson declined to comment.

Earlier this summer, the Senate rejected a similar bill to arm the Kurds fighting ISIS, with opponents citing White House concerns that such an effort would sow division within Iraq’s unity government.

It’s not the first time Washington has turned its back on the Kurds.

In 1991, President George H.W. Bush’s public suggestion that Iraqis “take matters into their own hands and force Saddam Hussein, the dictator, to step aside” encouraged a Kurdish and Shiite uprising against the Baathist regime. But when the uprising occurred, the Bush administration provided no support and thousands of Shiite and Kurdish Iraqis were slaughtered by the Saddam regime.