The cruelest irony of a U.S.-led coalition strike that mistakenly killed at least 62 Syrian forces is that rather than damage the Islamic State, as the strikes intended, the coalition may instead been a boon for the terror group.

The Syrian forces based near the eastern city of Deir el-Zour, the site of four strikes Saturday, were a buffer between the citizens of Deir el-Zour and the terror group. And if Syrian troops were hit by a coalition strike, it could lead them to retreat, creating an opening for ISIS to move onto a major city in eastern Syrian.

In recent months, ISIS has made an increasingly aggressive push for the city, putting Syrian government forces on the defensive. While ISIS has launched strikes against the airport, near the site of Saturday’s strikes, the airport has always remained under Syrian government control.

A defense official told The Daily Beast that U.S. Central Command now has concluded it was a mistaken strike and is trying to determine how it made such a big mistake.

The repercussions came swiftly. On Saturday evening, U.S. officials reportedly told their Russian counterparts that they reject the “unintentional loss of life,” essentially admitting responsibility for a strike. And Russia called for an emergency United Nations Security Council session Saturday night.

Around the region, some looked at the strike as proof that the United States created the ISIS threat and now is conducting strikes on its behalf.

“These attacks confirmed that the U.S. clearly supports the terrorism of Daesh,” said SAMA television, a Syrian state-run news outlet, using an Arabic acronym for the Islamic State.

What remains unclear is how the U.S. military could make such a mistake. A U.S. Central Command official told The Daily Beast that U.S. officials monitored the strike site, roughly 30 miles southwest of the city center, for two days before Saturday’s strike.

“There was a tank and other vehicles occupied by ISIS. There were people there who we thought were ISIS,” the CENTCOM official said.

In a statement from CENTCOM, which is in charge of the American effort in Syria, U.S. officials said they had been “tracking” what they believed to be an ISIS “fighting position… for a significant amount of time before the strike.”

But it was the Russians who first alerted the U.S. that it had made the mistake, forcing the U.S.-led coalition to abort its strike campaign, according to a U.S. Central Command statement, and admit it has been responsible for the attack around the airport.

Late Saturday local time, Russian Defense Ministry spokesman Maj. Gen. Igor Konashenkov said the U.S.-led coalition—using two F-16s and two A-10s—conducted four strikes near Deir el-Zour airport around 5 p.m. and had killed Syrian troops.

“The coalition airstrike was halted immediately when coalition officials were informed by Russian officials that it was possible the personnel and vehicles targeted were part of the Syrian military,” Central Command said in the statement.

Even before either side could confirm what precisely happened, combatants in the Syrian war began to spin the incident. The Russians, who first reported the strike, said the mistake showed why it was so important for the U.S. to coordinate with Assad’s biggest ally

The Russian defense minister spokesman also immediately noted such accidents could have been avoided had the U.S. and Russian coordinated their strikes over Syria, even as the U.S. said it had informed the Russians about the strikes. It is unclear how much time lapsed from when the U.S. informed the Russians and when it dropped ordnance.

“If these strikes were undertaken as a result of a coordination error, it will be because the Americans continue to refuse to coordinate with Russia regarding their actions against terrorist groups in Syria,” Konashenkov said.

The strike marks the first time the coalition has struck the forces of Bashar al-Assad, the dictator whom Washington has long threatened to depose—and long managed to avoid attacking. What’s more, it would mark a potentially illegal act by the United States in a country in which they have not been invited or declared war. The attack also strengthens Russian claims that the U.S. does not know what it's doing in Syria. From a tactical standpoint, the attack could put the Syrian army in a defensive posture until it can determine the U.S. motives behind the strike. And that could benefit ISIS, at least temporarily.

The U.S. is very familiar with Deir el-Zour. It has conducted scores of precise strikes around city, targeting ISIS and should know the city well.

Most notably, the U.S. conducted a raid in May 2015 in the area that killed a top ISIS financier, Abu Sayyaf, and captured his wife, Umm Sayyaf, who was believed to have held American hostage Kayla Mueller.

Konashenkov said Syrian officials had informed the Russians that at least another 100 Syrian troops had also been injured.

Of course, the U.S.-led coalition has struck the wrong targets before—often with deadly results. In January, the Pentagon admitted to bombing civilians on at least 14 different occasions. In July, an off-target airstrike in northern Syria killed more than 60 people. The U.S. has even come close to hitting its allies, nearly bombing American-backed rebel forces when it meant to target Syria’s affiliate in al Qaeda.

But to the Assad regime, the strike today was no accident. Damascus called it a "serious and blatant aggression.”

On Monday, the U.S. and Russia entered a ceasefire agreement in Syria, in part to get humanitarian aid to cities like Aleppo. The ceasefire does not apply to strikes targeting ISIS. How this attack will impact the ceasefire is so far unclear.