Foreign intervention in behalf of Syrian rebels U.S.-led intervention against ISIL The September 2016 Deir ez-Zor air raid was a series of 37 U.S.-led Coalition airstrikes near the Deir ez-Zor Airport in eastern Syria on 17 September 2016, lasting from 3:55 p.m. to 4:56 p.m. Damascus time in which Syrian Arab Army (SAA) soldiers were killed conducting operations against the Islamic State.

[8] The U.S. led coalition had been targeting ISIL militants in Syria since September 2014[8] although it has never coordinated any attacks with the Syrian government, whose President the U.S. had been trying to overthrow.

The agreement would have also seen the U.S. gain a veto, ensured by Russia, over the Syrian government's air force's combat missions over opposition and civilian-controlled areas, which at that time included the city of Aleppo.

[14] Those parts of the city and its outskirts controlled by the Syrian government were then effectively under siege by ISIL, leaving supplies to be solely delivered by transport helicopters.

A pro-Syrian government news outlet reported that on 17 September 2016, prior to the airstrikes, the Syrian Army was in control of Kroum hill and points 1 and 2.

[18][better source needed] At the time, the U.S. central command in Qatar was in communication with Russia, an ally of the Syrian government, via a special U.S.–Russia deconfliction hotline.

According to the U.S.'s investigation into this incident, this hotline was used for the first time on 17 September 2016 to inform the Russians about these impending airstrikes, which were planned to attack two target areas approximately 3 to 6 km southwest of the Deir Ezzor airfield.

[13] According to the U.S. coalition's investigation, the Russian operator "elected to wait to speak to their usual point of contact (POC) rather than pass the information immediately to the Battle Director" which "led to a delay of 27 minutes, during which 15 of the 37 strikes were conducted.

[20] In late September, Al Masdar News reported that the Syrian government said that 106 soldiers were killed at Jabal Thardeh by the Coalition, more than half of them in these strikes.

The ISIL attack allowed them to take control of Tharda mountain, which was seen as strategic as it looks over the government-held Deir ez-Zor military airbase.

[29] The attack triggered "a diplomatic firestorm", with Russia calling an emergency United Nations Security Council meeting in response to the incident,[5] during which both the U.S. and Russian ambassadors chastised each other.

In reference to the Deir ez-Zor attack, the spokesman said that "we have taken all the necessary measures to prevent any such 'mistakes' with regard to Russian servicemen and military facilities in Syria" and he further warned the U.S. coalition that in case of a perceived coalition threat to the Syrian military, the "Russian air defense missile crews will unlikely have time to clarify via the hotline the exact flight programme of the missiles or the ownership of their carriers.

"[36] The Syrian government released a statement saying that the air strikes were "conclusive evidence" of its long-held assertion that the U.S. and its allies were supporting ISIL and other jihadist groups as part of an effort to oust President Bashar al-Assad.

This claimed evidence can be exemplified by the Russian U.N. permanent representative's statements, as reported by a pro-Syrian government outlet, during the special U.N. security council meeting, which the U.S. envoy to the U.N. later referred to as "a stunt".

During the security council meeting, the Russian representative stated that "Russia believes the United States attack on the Syrian Army was not a mistake," declared that the "US Airstrike was intended to disrupt the ceasefire process and to drive the situation out of control," and suggested that "the airstrike has been conducted in order to derail the operation of the Joint Implementation Group and actually prevent it from being set in motion.

In light of the coalition's attacks at Deir Ez-zor, this led to concerns among Syria, Iran, and some Iraqi Shia groups, that the actual intent of the corridor was to effect an accumulation of these ISIL fighters around Syrian government troops at Deir Ez-zor so that ISIL would then attack and capture this city where proponents of this claim often indicate that this plot's purpose would be to reduce Syrian and Iranian government influence in the region by cutting the Shia Crescent.

Specifically, according to a Russian government news agency which was reportedly citing an unnamed diplomat, the concern was that "more than 9,000 Islamic State (IS, formerly ISIS, ISIL) militants will be redeployed from Mosul to the eastern regions of Syria to carry out a major offensive operation, which involves capturing Deir ez-Zor and Palmyra.

One of the conclusions of the report was that the attacks had been conducted "in good faith" that they were targeting ISIL militants and that they were consequently "in accordance with the law of armed conflict and the applicable rules of engagement for all nations involved."

The internal investigation, which interviewed "70 U.S. and coalition personnel" had "found no evidence of misconduct" and went on to list lessons to be learned from the airstrikes, including areas for improvement.