Armed men in uniform identified by Syrian Democratic Forces as U.S. Special Operations troops ride in the back of a pickup truck in the village of Fatisah in the northern Syrian province of Raqqa on May 25, 2016. (Delil Souleiman/AFP/Getty Images)

U.S. fighter jets scrambled to eastern Syria this week when Syrian bombers attacked in the vicinity of American and coalition Special Operations forces working with Kurdish and Arab opposition fighters, the Pentagon said Friday.

The unprecedented incident, near the Syrian city of Hasakah, did not result in a direct confrontation or any injury to U.S. or coalition forces.

But it illustrated the increasingly tense and ambiguous Syrian battlefield, where aircraft and ground troops from multiple countries — with multiple agendas and loyalties — are fighting overlapping wars.

Following the initial Thursday incident, the coalition began “actively patrolling the airspace nearby,” a Defense Department official said. Early Friday, “two Syrian SU-24 aircraft attempted to transit the area and were met by coalition fighter aircraft,” which “encouraged” the Syrians to depart “without further incident,” said the official, who spoke on a Pentagon-imposed condition of anonymity.

The Syrian military, engaged in a five-year civil conflict, has generally given a wide berth to U.S. aircraft targeting the Islamic State, as have Russian jets aiding their Syrian ally. But local fighters being assisted by U.S. Special Operations forces on the ground are often opposed to both the Islamic State and the government of Syrian President Bashar al-Assad.

“If the U.S.-led coalition think for once that by allowing them into Syrian airspace they can do whatever they wish inside, they are mistaken,” said a post on a Syrian Arab Army Facebook page. The Syrian Arab Army is the land element of Assad’s forces.

U.S. aircraft will defend coalition forces on the ground, a Pentagon spokesman said tersely, and Syria’s military “would be well advised not to interfere.”

Marine Maj. Adrian Rankine-Galloway said that the Syrian strikes targeted Kurdish forces in Hasakah on Thursday. Social-media reports indicated that several Kurds were killed in the bombing.

U.S. forces initially contacted Russia, using “deconfliction” channels established to ensure that Russian and U.S. planes over Syria avoid each other, but were told that the bombers in question were not Russian. Ground forces received no response to attempts to contact the planes through a recognized radio channel.

The United States then launched a “combat air patrol,” Rankine-Galloway said. It arrived in the area as the Syrian Su-24 ground-attack aircraft were leaving. While he would not specify from where the U.S. aircraft were launched, the United States maintains a contingent of F-15 fighter jets at Incirlik Air Base in Turkey.

The Syrian Arab Army’s Facebook page, which initially described the potential confrontation as an “interception” by the United States, later denied that there had been “any attempt at interception.”

Virtually all of northeast Syria is controlled by Kurdish forces and has remained mostly quiet since major fighting there, primarily between U.S.-backed Kurdish forces and the Islamic State, ended last year. Although the Syrian government has rarely been active in the area since the war began, Arab populations in the cities of Hasakah and Qamishli remain loyal to Assad, at least to the extent of mobilizing into quasi-governmental National Defense Forces (NDF) militias.

The two cities are divided between militia-controlled Arab and Kurdish portions, the latter held by the People’s Protection Units, YPG by its Kurdish initials. These Syrian Kurds have formed the bulk of the U.S.-backed Syrian Democratic Forces that have driven the Islamic State out of much of eastern and northern Syria and are being advised in the area by U.S., British and French special forces.

The partnership has been a continuing irritant in the relationship between the United States and NATO member Turkey, which considers the YPG an extension of Turkey’s Kurdish separatists, with whom Turkey is at war.

While frequent skirmishes have arisen in Hasakah and Qamishli between the YPG and the government-backed militias, “they haven’t escalated to a huge degree,” said Chris Kozak of the Institute for the Study of War. The government has a base outside Hasakah and operates an air facility at Qamishli; the YPG generally does not interfere with road travel between the two cities.

At the same time, Kozak said, “there are a number of U.S. Special [Operations] forces in the outskirts of Hasakah city, and several bases run by the YPG.”

According to the Syrian military, Kurdish forces this week “started an illegal arrest campaign against Arabs” in Hasakah, “who turned to the NDF for protection.” After an exchange of shelling, which eventually involved Syrian army forces, the government for the first time brought in airstrikes.

Individuals close to the Kurdish forces agreed that the clashes had escalated but said they began when the NDF began arresting Kurds.

The Kurds, the individuals said, think the government-backed moves are linked to a secret agreement between Assad and Turkey — which publicly backs U.S. insistence that a peace agreement in Syria is not possible until Assad leaves office.

Events during the week have also been cited to buttress additional theories about increasing Turkish cooperation with Russia after the healing of a rift between those two governments was consolidated by the visit of Turkish President Recep Tayyip Erdogan this month to Moscow, where he met with Russian President Vladi­mir Putin.

Syria’s “decision to escalate against the Kurds now makes me put more credence into rumors that Russia, Turkey and the [Assad] regime are now back-channeling a bit,” Kozak said.

“Russia had been flirting with the Kurds,” he said. “Now, with Turkey and Russia coming back together, that might be swinging the other way.” Turkey, Kozak said, “ranks the Kurdish threat above the Syrian regime threat.”

A senior Obama administration official, asked about the warming Turkey-Russia relationship, denied any concern and said that “we’ve welcomed the de-escalation of tensions” between them.

The official, speaking on the condition of anonymity under rules set by the White House to preview a visit of Vice President Biden to Turkey next week, said, “We don’t have any concerns that Turkey is somehow drifting away from the United States or NATO.”