Initial attacks and assault on the highway

On 22 May 2018, ISIL launched an attack, involving suicide bombers and armored vehicles, on a military outpost southeast of Palmyra and near the T-3 Pumping Station. Pro-opposition sources reported between 26 and 30 pro-government fighters were killed, including 17 non-Syrians, while the military denied the high death toll and put the number of dead at 16 soldiers.^[8][9] The next day, ISIL attacked a joint Syrian-Russian military convoy near the city of Mayadin. The ensuing clashes left 26 pro-Syrian government fighters, 5 Russian PMCs and 4 Russian regular soldiers dead. Russia reported 43 militants were also killed. Concurrently to the convoy attack, ISIL assaulted three Syrian military checkpoints in the same area. Three days later, two new ISIL attacks took place near Mayadin and Abu Kamal.^[10][11]

On 4 June, ISIL attacked government forces along a 100-kilometer front from Mayadin to Abu Kamal,^[12] capturing two or three towns on the western bank of the Euphrates.^[6][13] The militants attacked on two fronts, with ISIL fighters coming from both the desert, west of the Euphrates, and from their territory on the eastern bank of the river. A few days before the assault, around 400 ISIL fighters crossed the Euphrates from their enclave to the east following heavy shelling of government positions.^[6] The capture of the towns cut the Deir ez-Zor-Abu Kamal highway.^[14] The following day, pro-government forces recaptured the areas they had lost.^[12][13][15]

Attack on Abu Kamal

On 8 June, ISIL renewed its offensive^[16] and managed to break the Army's lines around Abu Kamal^[17] by using 10 suicide bombers,^[18] including several SVBIEDs.^[19] ISIL fighters managed to break into the city and fighting came close to the city center.^[17] The attack once again cut the highway.^[18] However, soon the Army launched a counter-attack and by the following day it was reported that the military managed to re-secure the city.^[20] During the fighting, the commander of the Syrian Army's 11th Tank Division, General Ali Muhammad al-Hussein, was killed in clashes on the outskirts of Abu Kamal.^[21] The commander of Hezbollah's Rocket Division was also killed.^[1] On 10 June, ISIL's offensive against Abu Kamal was still continuing,^[22] before the militants withdrew from the city on 11 June.^[7]