Palmyra offensive (December 2016)

Liwa Fatemiyoun militiamen gather outside of Palmyra on 10 December in an attempt to counter the ISIL offensive.

ISIL launched the offensive in the northeastern countryside of Homs on 8 December 2016, targeting the SAA's defenses near the village of Huwaysis and the Jazal Mountains located north of Palmyra. The group began the attack by sending two waves of fighters to storm its defenses near Huwaysis, resulting in heavy clashes. It was however unable to penetrate the first line of defense and was forced to withdraw. Local media reported that 60 militants were killed, while eight of their armored vehicles were destroyed.[35]

The group launched another assault later in the day, with simultaneous attacks near the Jazal, Mahr and Shaer oil and gas fields as well as the areas of Huwaysis, Arak, Palmyra Silos, al-Hayyal Mount, al-Sekkary, the ancient al-Hallabat Palace and an abandoned base near the T4 airbase. It was able to capture seven checkpoints from the Army, which withdrew after heavy clashes. In addition, it also captured the al-Hallabat Palace, al-Hayyal Mount, South Sawamea and Huwaysis. At least 34 pro-government fighters were killed and four, including an officer, were captured. With these advances, the group came within 4 kilometres (2.5 mi) of Palmyra.[49][50][51][52][53] The group also captured grain silos northeast of Palmyra[54] as well as the Jazal village and its oil fields.[55] Meanwhile, Combined Joint Task Force – Operation Inherent Resolve launched a massive air-raid on an Islamic State fleet of 168 oil tanker trucks, destroying them.[56]

The SAA counter-attacked on 9 December, to recapture the positions it lost the previous day, in addition to bringing in reinforcements and launching airstrikes. 15 soldiers were killed in an ISIL ambush near the Mahr oil field.[57] The Islamic State captured the al-Berej hills, Jihar oil fields, Mahr oil fields as well as a checkpoint near it during the clashes.[36][58]

On 10 December, Army reinforcements arrived in Palmyra.[59] At least 45 militants were killed by the Army, with three Islamic State tanks destroyed near Palmyra Silos. An earlier assault by the group on the silos had failed, but it was able to capture them later on, thus reaching the entrance to Palmyra. The Russian and Syrian Air Forces targeted ISIL positions in oil fields around Palmyra, destroying several armoured vehicles and a number of technical vehicles.[36][60] A Syrian Air Force MiG-23 crashed in the Jazal area. ISIL claimed to had shot it down,[61] while the Syrian Observatory for Human Rights (SOHR) reported it was not known whether it crashed due to technical fault or was shot down. Clashes also started taking place around Wadi al-Ahmar where the Army brought reinforcements.[62] The group later captured the Tar Mountain to the west of the city, in addition to the northern suburb of Amiriyeh, and entered Palmyra.[63] By the end of the day, they had captured most of the city, including Palmyra Castle,[64] and were on the verge of taking full control of Palmyra.[65] Palmyra's residents were evacuated in the evening by the Army.

Early on 11 December, after the arrival of reinforcements, the Syrian Army, backed by Syrian and Russian air units,[32] launched a successful counterattack to drive out ISIL forces from the city.[37] The militants withdrew to the orchards on the fringes of Palmyra. According to the Russian Ministry of Defense, ISIL suffered over 300 dead.[66] However, later in the day, ISIL launched a new assault on Palmyra after regrouping,[67] entering the city once again and capturing Amiriyeh, its hilltop and the Officers Housing complex.[68] Eventually, ISIL took full control of the city as the Army withdrew south of Palmyra.[2]

Liwa Fatemiyoun troops near Palmyra during the offensive

ISIL started advancing westwards from Palmyra to the Tiyas Military Airbase (also called al-Taifor and T4 airbase) after the city's capture on 11 December. The group captured two villages to the west of city during the day. It also captured an abandoned base to the west of the airbase.[64][69] Early on 12 December, ISIL launched an attack against the strategically important Jihar Crossroad near the airbase, and captured it after heavy clashes.[70] It later captured security checkpoints in the nearby districts of Mashtal and Qasr al-Hir,[47] allowing it to launch an attack against the airbase spearheaded by two car bombs, resulting in an hours-long battle with the entrenched SAA defenders. Aided by numerous Russian airstrikes, the government forces eventually repelled the assault, as ISIL forces regrouped for another attempt at breaching the airbase's defenses.[30] Meanwhile, hundreds of pro-government reinforcements arrived at the frontline, which belonged to the National Defence Forces-affiliated Qalamoun Shield[29] and Golan Regiment.[30] Russia carried out airstrikes against ISIL in Palmyra, killing five people.[71]

The group attacked the airbase again on 13 December, after advancing around it in an attempt to besiege it. Reinforcements from the Syrian Army and Russian special forces arrived to the base later in the day.[72][73] During the day, ISIL advanced on a checkpoint on the road to Al-Qaryatayn,[74] eventually capturing it and cutting the road. The road was a main supply route for the Syrian Army in Homs Governorate and had been used to supply military reinforcements to the airbase as well as Homs city from Al-Qaryatayn.[75] Meanwhile, an assault by the militants on the Tiyas pumping station during the night was repelled.[76] The clashes renewed on 14 December, with the Army trying to regain areas it previously lost around the airbase.[77][78] The Army recaptured the Tiyas Mountain as well as the abandoned base located in the north of the airbase after launching a counteroffensive during the early morning.[76] It also regained checkpoints on the road to al-Qaryatayn it had lost a day earlier.[79] ISIL meanwhile captured al-Sharifah village to the west of the airbase.[80] Later that day, ISIL launched another attack on the airbase, but thanks to newly arrived government reinforcements, belonging to the paratrooper forces of the Republican Guard's 800th Regiment, the assault was repelled. The following night, a SAA counter-attack drove ISIL from the airbase's outskirts.[28][81]

The US-led coalition stated on 16 December that it had carried out airstrikes near the airbase against ISIL on the previous day, destroying the heavy weaponry it seized after recapturing Palmyra. An air defense artillery system, 14 tanks, three artillery systems, two ISIL-held buildings and two tactical vehicles were destroyed in total. The strikes reportedly killed at least 38 militants.[82][83] The Syrian Army launched another counterattack on 16 December, recapturing the Qaryatayn-T4 crossroads area.[84] They later also recaptured the road between al-Sharifah and al-Qaryatyn and reopened the direct route between al-Qaryatayn and the airbase. Umar As'ad, a leader of ISIL, was killed in the clashes.[17][18] The Army recaptured a checkpoint near al-Qaryatayn on 17 December.[85] Another attack by ISIL later in the day was repelled, while the Army captured Al-Sha'arah Hills to the north of the abandoned base.[86] ISIL launched another attack on the airbase on 19 December and shot down a Russian helicopter.[87] The attack failed with 36 ISIL fighters being killed.[88] At least 20 pro-government fighters were killed in it while a helicopter was shot down, leaving its two pilots dead.[89] Clashes took place between the two sides on outskirts of Abu Kala Dam as well as other areas near the airbase on 20 December.[90] ISIL was also repeatedly attacking the abandoned base in order to retake it.[91] On 22 December, ISIL launched another attack in the morning, which failed. The militants launched another assault later on, which was also repelled. The group was then driven back to Palmyra.[1] At the same time, a US airstrike killed the leading ISIL commander for the Palmyra frontline, Amr As'ad.[14]