[3] After another two months of fighting, the Syrian Arab Army captured the IS-held parts of Deir ez-Zor city and its environs, by 17 November 2017.

In April 2014, following their defeat at the hands of the rebels, ISIL returned and launched a large-scale offensive against the Syrian rebel groups in the Deir ez-Zor Province, expelling them from the area, and allowing ISIL to gain control of most of the Deir ez-Zor Governorate and besiege the remaining Syrian Government forces, in July 2014.

From early to mid-September 2014, ISIL made several unsuccessful attempts to breach the Deir ez-Zor military air base.

[55] In September 2015, ISIL started regularly to shell the airbase, severing the air bridge that had supplied the city with food and other goods.

[59] After a few days of heavy fighting, ISIL overran the Baghiliya and Ayyash neighborhoods,[citation needed] after which pro-government fighters and their families were among those targeted in the seized areas.

The Syrian government and state media said that 250[60]–300[61] people were killed, including some by beheading;[60] the British-based SOHR had differing numbers, reporting 135 fatalities,[61] of which 85 were civilians and 50 soldiers.

[65] Between April and May 2016, back-and-forth fighting took place as ISIL attempted to advance against government troops in the Industrial and al-Sina'ah districts of Deir ez-Zor city.

[67][68] In July 2016, pro-government sources said that heavy Russian air-strikes against ISIL managed to relieve the pressure on Syrian Army troops stationed on the mountain.

[69][70] On 17 September 2016, a series of 37 U.S.-led Coalition airstrikes near the Deir ez-Zor Airport,[71] lasting from 3:55 to 4:56 p.m. (Damascus time),[72] killed 90 Syrian Army soldiers and wounded 110 more.

[80] After two days of fighting, ISIL succeeded in cutting the road linking the air base to the city,[81] leaving the government enclave split in two.

[86][87] Also, late that month, ISIL conducted a tank assault on the government-held Al-Fourat university, located on the N7 Highway leading to the provincial capital.

[89][90][91] Towards the end of May, Army forces were still staving off attacks by ISIL fighters, while 100,000 civilians were surrounded and living without adequate food, services or safety.

[109][110][111] During May and June 2017, the Syrian Arab Army established control over most of the southern part of Raqqa province, as well as the Eastern Qalamoun Mountains.

In mid-July, Syrian forces launched a campaign in Central Syria targeting ISIL strongholds in the provinces of Homs and Hama.

[112] In the morning of 29 August, the Syrian forces launched a surprise attack in the western part of Deir ez-Zor, targeting ISIL's positions in the strategic Panorama area.

[113] On 31 August, the Syrian Arab Army established full control over the strategic mountain of Bishiri, west of Deir ez-Zor city.

[114] Syrian and Russian aviation carried out a joint air attack on an ISIL command center in the al-Rashdiyah district of Deir ez-Zor.

[115] By 31 August, the Syrian Army, headed by elite Tiger Forces, had advanced to within 50 kilometers of Deir ez-Zor from Sukhna in the east.

[120] The breaking of the ISIL siege of the city was met with scenes of celebration as civilians exchanged congratulations and fired celebratory gunshots into the air.

According to one resident, people would "prefer the government over Daesh" in the hopes that breaking of the siege could mean the gradual return of life to Deir ez-Zor, and along with it basic supplies.

[122][123] On 17 October, the Syrian Army said it had secured a perimeter surrounding the ISIL-controlled half of the city, encircling the remaining ISIL forces in eastern Deir ez-Zor.