SILOPI, Turkey— Fighters from the Islamic State were coming. Already, the militants had cut a bloody path through Syria and western Iraq; bragging about executing security forces and slaying civilians. Now they were advancing north, ransacking mosques and churches, and sending hundreds of thousands of people fleeing into the forbidding Sinjar Mountains.

The Iraqi army had all but folded. The Kurdish militia known as the Peshmerga were running low on ammunition and morale. Washington had yet to act.

But one group — designated a terror organization by both the United States, the European Union and Turkey — were coming to the aid of the fleeing minority Yazidis. Today, many of those who survive credit the fighters with saving them from genocide.

“They saved us, as our Arab neighbors helped [the Islamic State] try to kill us,” one man said recently at a camp in southeastern Turkey. Many others echoed his remarks.

A PKK banner at a refugee camp in southern Turkey, August, 2014.

The Marxist-leaning group, the Kurdistan Workers Party also known as the PKK, for decades has fought for an independent Kurdistan, sometimes taking hostages or conducting arson attacks, and killing thousands of people, including civilians,

But now, the group appears to be gaining more acceptance.

At camps in southern Turkey now sheltering more than a thousand Iraqi refugees, flags bearing the image of the group's jailed leader, Abdullah Ocalan, hang proudly above their tents. Inside, people rave about the brave fighters who defended them from evil, ushering them through the mountains to safety when they were otherwise left to fend for themselves.

The PKK has been on U.S. terror lists since 1997 for its bloody campaign against Turkey for Kurdish autonomy. Recently the group entered a ceasefire with the Turkish government and turned its sights on jihadi fighters operating across the border in Syria.

A Kurdistan Workers Party (PKK) fighter guards a post flying the PKK flag in Arbil, Iraq, on August 21, 2014. Image: AHMAD AL-RUBAYE/AFP/Getty Images

Since then, a petition to remove the group from the United State's list of terror organizations has racked up more than 30,000 signatures. And several European politicians have raised the issue for debate.

The Center for American Progress, a left-leaning Washington think tank, had already published a report calling for the U.S. to reevaluate its relationship with Kurdish militant groups before the dramatic rescue of the Yazidis.

“It's important to look around the region and consider, who could we work with here?" said Max Hoffman, one of the authors of the report. "You can't afford to totally ignore the Kurdish groups.”

While Hoffman acknowledges the PKK's bloody past, he points out that the group has made major strides toward political legitimacy in the last decade.

An elderly PKK fighter bears his riffle, comes back to the PKK base in Makhmour from a patrol. Makhmour is a town located 50 kilometers South of Erbil. Image: Vianney Le Caer/Pacific Press/LightRocket via Getty Images

But some question whether the portrayal of Kurdish militants as key players in the fight against the Islamic State is entirely warranted.

David Pollock, a senior fellow at the Washington Institute for Near East Policy, characterizes their role as mostly defensive. “The actual battle was — and continues to be — mostly Peshmerga," he said. "They have their top commanders engaged and best units on the ground.”

Also, Pollack cautions that reports of significant PKK presence in Iraq — both in the rescue of Yazidis and in battles against jihadi fighters — could be exaggerated or confused. Even on the ground, it's not easy to distinguish between Kurdish groups, Pollack said.

Kurdistan Workers Party (PKK) fighters guard a post bearing an image of jailed PKK leader Abdullah Ocalan.

The PKK is currently communicating with the Turkish government to forge a path to peace—something the country's president and prime minister have singled out as a top priority.

Though still widely despised in Turkey for their 30-year campaign, hopes are high that its negotiations with the government could finally put the conflict to rest. Exactly how the PKK's role in fighting the Islamic State will affect those peace negotiations, however, remains to be seen.

So far, Washington has not shown any serious signs of changing its stance toward the PKK. But if a proposal to partner with the PKK to counter the Islamic State was raised, experts agree that the U.S. would ultimately defer to Turkey, an important NATO ally.

Kurdistan Workers Party (PKK) fighters guard a post as they participate in an intensive security deployment against Islamic State (IS) militants in the town of Makhmur, southwest Arbil. Image: AHMAD AL-RUBAYE/AFP/Getty Images

Whatever happens in Ankara or Washington, the secular-minded PKK fighters will likely keep taking the fight to the Islamic State — especially after the radicals recently bragged of beheading a Kurdish fighter.

“The Kurds are not going to roll over and take that,” Pollack from the Washington Institute said. “They're going to fight back very hard.”