The Pentagon (Stars and Stripes)

WASHINGTON — The Pentagon is reviewing how it targets Islamic State militants for attack after forces aligned with the Syrian government were mistaken for terrorists and killed in an airstrike this summer, U.S. Central Command announced Tuesday.

“We had no intent to target Syrian forces,” Air Force Brig. Gen. Richard Coe, the officer who led the investigation into the incident, told reporters Tuesday at the Pentagon. “… In many ways, the group looked and acted like the (Islamic State) forces we have been targeting for the last two years.”

Coe said he could not “definitively conclude” who was killed in the airstrikes, but evidence suggests the targets were forces backing the regime of Syrian President Bashar Assad.

The airstrike, which took place Sept. 17 just south of Deir al-Zour, was an “unintended, regrettable error” but it did not violate international law and it followed proper rules of engagement, Coe said.

Coe’s investigation concluded at least 15 people were killed and “likely dozens more.” The Syrian Observatory for Human Rights estimated nearly 90 people died.

Though the United States does not target Syrian government forces, President Barack Obama has said he wants to see Assad step down as president of Syria, which has been embroiled in a bloody civil war for more than five years.

The strike is the only known attack to include U.S. aircraft alleged to have killed Syrian government-aligned forces, according to defense officials. Australian, British and Danish aircraft were also involved in the strike.

The U.S.-led Operation Inherent Resolve coalition was certain it was attacking the Islamic State group after monitoring the forces from the sky for about two days, Coe said.

The fighters were not wearing military uniforms or displaying flags or other identifying insignia, he said. Additionally, they displayed “friendly” interactions with other groups in an Islamic State “area of influence.”

Coe blamed the errors largely on “human factors,” including miscommunications and an optimistic view of the intelligence.

The strike occurred about two days after the coalition began watching a vehicle suspected of carrying Islamic State fighters. Coalition war planners began preparing for a deliberate strike, a process where a specific target is hit after several days or weeks of monitoring. But after officials viewed the vehicle interacting with several other groups believed to be part of the Islamic State group, the plan shifted to an opportunistic — or dynamic — targeting process.

However, at least one intelligence analyst concluded before the airstrike that the forces being targeted could not have been the Islamic State group, Coe said. But that information was never relayed to decision-makers after other analysts concluded they were Islamic State militants.

A group of F-16s, F/A-18s, A-10s and drones dropped 34 precision-guided bombs and shot 380 rounds of 30-millimeter ammunition at the target before the strike was abruptly halted after the Russian military advised the coalition that it was shooting at Syrian government forces.

The strike should have ended earlier, Coe said. The Russians, who back the Assad regime, delayed reporting the errant strike to the coalition for 27 minutes because they were unfamiliar with the officer who answered the hotline that the two countries use to avoid mishaps in the skies over Syria. During that delay, 15 bombs were dropped.

U.S. forces also mistakenly relayed inaccurate coordinates to the Russians, which stopped them from alerting the Syrian forces in the area, Coe said.

The majority of Coe’s investigation report is classified. The general did recommend the coalition review its targeting processes. The coalition has already begun that review, said Air Force Col. John Thomas, a spokesman for CENTCOM.

Additionally, Coe recommended the coalition implement so-called “red team” intelligence officials to offer an opposing view of collected intelligence to decision-makers and to improve its information-sharing and mission-review processes.

dickstein.corey@stripes.com Twitter: @CDicksteinDC