In 1940 the anthropologist Henry Field identified Hajin as the location of the tribal confederation Al Bu Hardan under a chief named Manawakh al Khalil and he denoted them as charid owners. A charid is described by Field as being a device used to pull water up steep banks under the labor of livestock so that it can be used for irrigation.
The city came under the occupation of the Islamic State of Iraq and the Levant in 2014 during the Syrian Civil War. In late November 2017, Hajin became ISIL's de facto capital city after they lost their Raqqa, Mayadin, Al-Qa'im, and Abu Kamal strongholds at the hands of the Syrian government, Iraq, and Kurdish-led forces respectively. On December 28, 2017 the Syrian Democratic Forces reached the city of Hajin and began a campaign to remove ISIL. This action was a part of the SDF's Operation Cizire Storm. In 2018, Iraqi intelligence and some experts believed that ISIL leader Abu Bakr al-Baghdadi was hiding in Hajin, due to the concentration of ISIL forces and leadership in the city, even though there has not yet been any direct evidence that al-Baghdadi himself was present there. In March 2018, the SDF paused the campaign against Hajin in order to defend Afrin from the invading Turkish Army, but the operation resumed by 24 April 2018. On June 22, 2018, coalition forces led by the U.S. dropped leaflets on Hajin and in the Abu Khater area. On September 10, 2018, the SDF launched an offensive to take Hajin and its surrounding area. One news report estimated that around 4,000 ISIL fighters were defending the city, though other reports put the number of ISIL fighters between 1,500 and 2,500. On August 22, 2018 the Islamic State attempted a counterattack to break the siege of Hajin but was repelled. On September 11, 2018 the SDF advanced on Hajin with US-coalition support. On October 31, 2018 the SDF suspended its operation in Deir ez-Zor, including their efforts against ISIL in Hajin, as a response to Turkish attacks against SDF-held areas in northern Syria. On December 4, 2018, after resuming their offensive against Hajin the SDF entered the town and started their battle against ISIL for control of the city. On 14 December 2018, the SDF spokeswoman Lilwa al-Abdallah said that the military operations are ongoing to fully end ISIL and soon, we will celebrate the full liberation of Hajin. It said small pockets of ISIL resistance will be suppressed in the next two days. Hajin was captured in December 2018. of the Abu Kamal District.
