The president of Iraqi Kurdistan on Friday slammed the United States-led coalition against the Islamic State in Iraq and the Levant (ISIL) for excluding the Kurds from an organizational meeting in London this week, noting that his hard-bitten peshmerga fighters had proven themselves the only capable force on the ground to combat the armed group.

“We were expecting everyone to show respect to the sacrifices made by the people of Kurdistan and its peshmerga [fighters] by inviting a representative from Kurdistan to this event and similar such events,” Massoud Barzani said in a heated statement, as translated by Kurdish Rudaw news.

The peshmerga “are the most effective force countering global terrorism today," he added. “It is unfortunate that the people of Kurdistan do the sacrifice and the credit goes to others."

It’s not clear why the Kurds were snubbed at the London conference, though many suspect it could simply be a matter of diplomatic protocol. Leaders from 21 countries involved in air strikes on ISIL targets across Syria and Iraq were present, including Iraqi Prime Minister Haider al-Abadi. Inviting a regional leader like Barzani would have been an exception.

But Barzani's disappointment is understandable. Since ISIL surged from its base in Syria to seize swaths of Iraq last summer, the Kurds have successfully defended their autonomous homeland in the north from the extremists. They have even been effective on the offensive, most critically on the outskirts of Mosul, Iraq’s second city and ISIL’s most important holding in the country. Just a day before the London conference, peshmerga forces launched an offensive just west of Mosul, killing approximately 200 ISIL insurgents, the Kurdish Regional Government (KRG) said.

The Kurds have paid a steep price for their aggressive bearing: As of mid-December, more than 700 peshmerga fighters had fallen, according to KRG numbers.

The underpowered Iraqi military, meanwhile, has wilted before the ISIL onslaught, with reports of entire battalions abandoning their posts and even stripping off their military uniforms to avoid detection. ISIL has been known to summarily execute enemy combatants by the dozens.

All the while, coalition members including the U.S. have sent the Kurds mixed messages, said Gonul Tol, director of the Center for Turkish Studies at the Middle East Institute in Washington, D.C. Over the past seven months, the U.S. and its allies have offered unprecedented military aid to Kurdish forces in order to pressure ISIL on the ground. The Kurds, Tol said, may have perceived this support as a sign that the U.S., which has long discouraged the Iraqi Kurds’ ambitions of independence from Iraq, could be shifting gears. A State Department representative even attended an oil conference in London that featured Kurdish representatives (independent Kurdish exports of oil have long been frowned upon by the U.S., seen as an affront to the central Iraqi government).

“The Kurds thought this could be their moment, that the rise of IS [ISIL] would be a historic moment for Kurdish independence,” said Tol. “There was this idea that the Kurds could be the best alternative to IS [ISIL] because they’re secular and pro-Western.”

Most surprisingly, the U.S. even airdropped arms to the Syrian Kurdish PYD militias defending the besieged town of Kobani from ISIL last year, in a bid to pressure Turkey to open its borders and allow the PKK — the PYD’s Turkey-based partners who both Washington and Ankara deem a "terrorist" organization — to enter the fight. There has even been talk in Congress of delisting the PKK from the U.S. "foreign terrorist organization" list, given their role in rescuing threatened Christian and Yazidi minorities from ISIL onslaught.

But Tol said these deviations from U.S. policy may be more readily regarded as a matter of necessity. "This doesn’t mean there’s a new strategy of the U.S. supporting Kurdish independence," she said. Not inviting the Kurds to London signifies "we still want a unified Iraq, and Baghdad is the real representative.”

Still, the very fact that the coalition is forced to skirt around direct coordination with their most important ground partners points to a strategic dilemma for the U.S and its allies, said Wladimir van Wilgenburg, an expert on Kurdish politics with the Jamestown Foundation.

“It’s a little bit illogical,” said van Wilgenburg, who spoke from the Kurdish regional capital of Erbil. “Especially if they hope to defeat ISIL in Mosul — the most important symbol and base for IS [ISIL] in Iraq — they’re going to need the Kurds.”