Members of Jabhat al-Nusra Front carry their weapons as they move towards their positions during an offensive to take control of the northwestern city of Ariha from forces loyal to Syria’s President Bashar al-Assad, in Idlib province May 28, 2015. (Reuters/Ammar Abdullah)

Jabhat al-Nusra, the al-Qaeda affiliate in Syria, has disclosed that it suffered heavy casualties when the U.S. launched drone attacks last month to defend a moderate opposition group called “Division 30.”

“The U.S. strikes caused some of our dear brothers to be granted their martyrdom and others got wounded,” wrote a Dutch fighter named Abu Mohammad al-Hollandi, in a Twitter posting on July 31, the day of the battle. “We from Nusra decided to make a tactical retreat & thus minimize the possible casualties that could fall because of these strikes.”

Jabhat al-Nusra actually lost between 30 and 40 fighters to the U.S. bombing strikes that day, according to one official involved in the operation to train and equip Division 30. He said the al-Qaeda affiliate had suffered a 5:1 kill ratio in its pre-dawn July 31 assault on Division 30. This lopsided casualty rate encouraged potential recruits to the “New Syrian Army,” as the moderate force is known, that the U.S. and allies is serious about defending its allies, the official said.

This new information paints a less bleak view than what I described in an Aug. 20 column about a “chain of errors” in the Division 30 saga. While U.S. officials concede there were planning and intelligence mistakes, they say the showdown with Jabhat al-Nusra may have ended as a net plus for Syrian moderate forces. By using drones so aggressively, the U.S. showed it was prepared to fight back after reversals.

Postings by Jabhat al-Nusra members help illuminate what happened in the days after 54 U.S.-trained Division 30 fighters were sent into the Syrian border region of Azaz, north of Aleppo, around July 12. Because the opposition group’s target was the Islamic State, U.S. commanders hadn’t expected that Jabhat al-Nusra would attack. But it did — first in a July 29 kidnapping of seven fighters, then in the July 31 assault.

A Jabhat al-Nusra statement explained the kidnapping as a kind of reconnaissance. “It was incumbent on the Nusra Front to investigate and take caution and be wary of such projects,” said the statement, which was published by the SITE Intelligence Group. “It [Nusra] arrested a number of soldiers in the Division, and the reality of their project was proven to the Front; that they are agents to bring about the projects and interests of America in the region.”

The Dutch fighter al-Hollandi explained separately: “After interrogation it became clear for Nusra what this filthy US backed group was up to. And it became clear that the US command center had direct contact with the commanders of ‘Division 30,’ thus making it for the US easy to immediately react with their drones and fighter jets.”

The attack on Division 30 was intended as “a hit and run attack [to] teach them a lesson that we won’t tolerate any group that fights for a foreign country and with a western agenda,” said al-Hollandi.

The battlefield in northern Syria is confusing because Jabhat al-Nusra, until recently, has been a leader in fighting the Islamic State. Yet Jabhat al-Nusra announced in an Aug. 9 communique that it was withdrawing its fighters from battle zone against the Islamic State north of Aleppo (termed by U.S. commanders the “Mar’a Line”) because it didn’t want to collaborate there with the U.S. and Turkey. But a coalition official said moderate fighters had filled in the gap left by the departing Jabhat al-Nusra, and that heavy air attacks by the U.S. and its allies had pounded the Islamic State along the Mar’a Line in recent days.

For Jabhat al-Nusra, this appears to have been a tactical retreat. Explained the Aug. 9 communique: “Faced with the current scene, we could only withdraw and leave the points of our vigil with the renegades in the northern Aleppo countryside to be taken over by any fighting faction in those areas.”

The aggressive drone attacks may explain why, despite initial reversals, a Division 30 commander named Abu Iskandar told Al Aan TV reporter Jenan Moussa on Aug 20 that, in her words, “he doesn’t bear any grudge against the U.S.” Evidently, American firepower eases the pain of U.S. intelligence and planning mistakes.