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In the recent days, Syrian opposition websites have reported that Iran has reinforced its presence in the Al-Bukamal area in eastern Syria, near the Iraqi border. Iran ascribes strategic importance to eastern Syria, since this region completes the territorial continuum stretching from Iran to the Mediterranean. Moreover, U.S. forces are concentrated in that region, east of the Euphrates, so control of it can provide Iran with leverage vis-à-vis the U.S. Hence, since 2017 Iran has been making efforts to consolidate its presence there, chiefly by means of the Shi’ite militias loyal to it.
According to recent reports, Liwa Al-Fatimiyyoun, an Afghan Shi’ite militia loyal to Iran’s Islamic Revolutionary Guards Corps (IRGC), has reinforced its troops in the Al-Bukamal area in eastern Syria. A report from April 29, 2020 stated that the militia’s forces had deployed along the Euphrates river with the aim of launching an attack “within hours” on positions of the U.S.-led International coalition on the opposite bank of the river. Another report stated that IRGC Aerospace Commander Amir Ali Hajizadeh recently visited the Al-Bukamal area.
The following are details from recent reports about location and movements of Liwa Al-Fatimiyyoun:
On April 29, the Euphrates Eye website reported, citing a “special source,” that 30 military vehicles had arrived in Al-Bukamal from Iraq in the previous two days, carrying about 100 members of the Imam Al-Hassan faction of Liwa Al-Fatimiyyoun. These militiamen, it said, deployed along the Euphrates near Al-Bukamal bridge, in positions that had been prepared one month earlier and equipped with munitions of various types. The website claimed to have information that the Imam Al-Hassan faction planned to launch an attack coalition positions within hours. 
The Al-Bukamal bridge area (source: Facebook.com/euphrateseye, April 29, 2020)
Earlier that day, the Sada Al-Sharqieh opposition website reported “an unprecedented military state of alert” in the Al-Bukamal area and that all the roads leading to the Syria-Iraq border had been closed. This report stated further that IRGC Aerospace Commander Amir Ali Hajizadeh had arrived in Al-Bukamal via the Al-Qaim border crossing and had surveyed the area with other Iranian officers before returning to Iraq.
According to an April 24 report on the website of Syria TV, an opposition channel broadcasting from Turkey, hundreds of Al-Fatimiyyoun operatives have entered Syria via its land borders this month and have deployed in various parts of the country, but especially in the Syrian desert and in the Aleppo, Idlib and Deir Al-Zor regions. The report also claimed that many of the operatives had arrived with their families, presumably in order to settle in the areas under the control of the regime forces and the Iran-backed militias in Palmyra and eastern Homs, as well as in the Al-Bukamal area, southeast of Deir Al-Zor on the Iraqi border.
Liwa Al-Fatimiyyoun logo
This report also listed locations where the militia forces are present. In the Aleppo region, they have several positions around the Iranian military base in the Jabbal Azzan area south of the city. They are also present at the air force technological academy and the munitions and artillery academy in western Aleppo, and north of the city they have positions near Aleppo Industrial City – Sheikh Najjar and in the area between the Central Prison and the Infantry School.
In eastern Syria, the militia forces have a significant presence in the Palmyra desert, east of Homs. In the last few weeks, following surprise attacks by ISIS on Iranian militias, they have taken up numerous positions in this region, including in the Al-Sukhnah area, along the Deir Al-Zor-Homs road.
 On Iran’s presence in eastern Syria, see MEMRI Special Dispatch No. 7790, Syrian Opposition Websites: Iran Consolidating Its Presence In Eastern Syria, West Of Euphrates, To Form Continuum From Iran, Through Iraq And Syria, To Mediterranean, December 4, 2018.
 Facebook.com/euphrateseye, April 29, 2020.
 Facebook.com/SadaAlSharqieh, April 29, 2020.
 Syria.tv, April 24, 2020.