The proverb "the enemy of my enemy is my friend" is as well known in Arabic as it is in English. In Syria, where a struggle to oust President Bashar al-Assad has devolved into a bloody multidimensional conflict between moderate rebels, Islamist extremists, Kurds, and the government, the phrase is dizzying to contemplate.

Usama, a teacher from Aleppo, laid this bare for me some nights ago, in a series of furtive messages he sent via WhatsApp from the shipping container he uses as shelter at the Kilis refugee camp in Turkey on the Syrian border. As far as he's concerned, Assad is the only enemy — and he would willingly join up with the Islamic State (also known as ISIS) if the terrorist group has the best shot at eliminating him.

The war interrupted Usama's university studies, and government helicopters shelled and devastated his house. His brother joined the Free Syrian Army and has been shot ten times, most recently in the neck. When I met Usama six months ago, he was supporting the revolution by teaching in a school run by the opposition. He showed me pictures of the dozens of students killed by barrel bombs.

Amid the war's conflicting interests, Usama believes in only one policy goal: "Kill fucking Assad." But in Aleppo, the moderate opposition's most important front, the rebels are losing. Now Usama wants to take up arms, and he wants to join the side with the greatest advantage.

"I am gathering some people to fight," he told me, "and ISIS is strongest now."

Recruiters of various stripes are working to bring fighters from refugee camps to their side of the war — and Islamic State recruiters are said to be the most organized.

I later received a press release from the National Coalition for Syrian Revolutionary and Opposition Forces that acknowledged this sentiment. It criticized the international coalition against the Islamic State that was formed by the United States, Saudi Arabia, Qatar, and others, because the strategy excludes aggressive military support for the fight against Assad. The opposition government warned that moderate fighters in Syria would join the Islamic State as a last resort if they don't get military support soon.

The morning after hearing from Usama, I met with Muhammed Qaddah, the vice president of the National Coalition, in a cavernous restaurant near Istanbul Ataturk Airport. He is a veterinarian from Dara'a, and unlike some other members of the opposition government, he participated in the early days of the revolution.

Qaddah was in northwest Syria in September when US-led airstrikes hit Idlib Governorate, targeting militants but also killing civilians. Locals reacted by calling for the Islamic State to intervene, he said. He showed me a video of protesters holding a banner that read, "Obama: Now we are either under Tomahawk missiles or Assad's barrels." They marched in the dark, chanting their welcome to the Islamic State.

The civilians are not extremists, Qaddah said, but they have no viable options. He noted that Western-backed fighters in Idlib had recently lost ground to the al Qaeda affiliate Jabhat al-Nusra.

The international coalition's military aid for the Kurds fighting in Kobane is a point of rancor to Qaddah. The Syrian opposition alleges that the Kurdish fighters receiving "selective" US military support — the People's Protection Units, known as the YPG — are allied with Assad. The animus is mutual: the YPG accuses the opposition of yielding to undue influence from Turkey's government, which considers YPG a terrorist organization.

Qaddah drew a map of the Free Syrian Army's positions in Aleppo and the northern countryside. Under cover of the international coalition's airstrikes campaign, he said, both the Syrian government and Islamic State forces are stepping up attacks on supply corridors between the Turkish border and Aleppo. If the Islamists take Aleppo, moderate fighters who refuse to join them "will be slaughtered," he said.

Many Turks and Syrians know the significance of a shared enemy, but some worry that the American government does not. US foreign policy in Syria lurched into action this summer after ISIS made quick-paced territorial gains in Iraq and rebranded itself the Islamic State. President Barack Obama watched as a Sunni insurgency in Iraq reawakened demons of the disastrous war that he built his candidacy campaigning against.

The great contradiction of US policy in Syria is the fact that it is striking against one of the main opposition groups to Assad — the Islamic State — while not directly striking against Assad's forces. While it's clear to US officials that weakening the Islamic State bolsters Assad in Syria, as Obama remarked of the Islamic State and other radicals on 60 Minutes, "Those folks could kill Americans. And so… there's a more immediate concern that has to be dealt with."

To Qaddah, the worst slight is that the Syrian opposition government is not included in the international coalition against the Islamic State.

"We have our own military conference, our own army," he said. "Why should we not participate? It's our country!"

The US supports training for moderate fighters in Syria, but it appears that it moves faster against an enemy than in support of a friend.

Recruiters of various stripes are meanwhile working to bring fighters to their side of the war in the refugee camp where Usama is staying. He believes that the Islamic State recruiters are the most organized.

Most of the camp's residents are from the countryside of Aleppo, and are quick to lend an ear to members of a group that can deal a fatal blow to Assad.