The Syria Comment version of his article has several additional photos and captions.
Fighters posing with the flag of Liwa al-Imam al-Mahdi. Bottom: "The Imam Ali Battalion. The Islamic Resistance in Syria." Note the classic arm and rifle associated with Hezbollah. Top: "Indeed the party of God are the ones who overcome" (Qur'an 5:56), a play on "Hezbollah" (Party of God).
The Syrian civil war has seen the rise of a number of formations that promote the idea of building a native Syrian Muqawama Islamiya ('Islamic Resistance') and Hezbollah. Examples include Quwat al-Ridha (recruiting mainly from Shi'a in the Homs area), the National Ideological Resistance (based in Tartous/Masyaf area), the Ja'afari Force (recruiting mainly from Damascene Shi'a) and al-Ghalibun.
Liwa al-Imam al-Mahdi (the Imam Mahdi Brigade), referring to the twelfth Shi'i Imam, is another group along these lines. For comparison, the National Ideological Resistance also has the label Jaysh al-Imam al-Mahdi (The Imam Mahdi Army).
Liwa al-Imam al-Mahdi appears to have at least two sub-components: the Imam Ali Battalion and the Special Operations al-Hadi Battalion. The al-Hadi Battalion claims at least two squadrons: the first led by "al-Saffah" and the second led by "Abu Ali Karar."
The information available on Liwa al-Imam al-Mahdi through social media is patchy at best, but I was able to speak to the commander of the Imam Ali Battalion, who goes by the name of al-Hajj Waleed and is from Ba'albek in the Beqaa Valley in Lebanon.
Left: Abu Hadi, the leader of the al-Hadi Battalion. His real name appears to be Rani Jaber and he is Syrian (from Deraa). Right: Liwa al-Imam al-Mahdi fighters prepare for "the battle of the north" (according to the source posting this photo in early June), likely referring to fighting in Aleppo.
According to al-Hajj Waleed (who is a member of Hezbollah), Liwa al-Imam al-Mahdi was set up two years ago by Hezbollah and has recruits from all of Syria.
Of course, this latter assertion is a fairly standard rhetorical line. Private Facebook accounts run by those associated with Liwa al-Imam al-Mahdi largely point to origins in western Syria.
The commander added that the group has participated in a number of battles, including Deraa, Quneitra, Ghouta, Aleppo and the Ithiriya-Raqqa route. Some of these operations (e.g. fighting in south Aleppo countryside and positions on the Ithiriya hills) have been mentioned on social media.
In total, Liwa al-Imam al-Mahdi's contribution to the fighting in Syria seems similar in scale to that of the Ja'afari Force and the National Ideological Resistance. Al-Hajj Waleed gave his toll of killed ('martyrs') and wounded at 25 and 55 respectively.
Thus, the military capabilities of these groups should not be exaggerated, but it is apparent how Hezbollah is trying to project influence into Syria through the creation of multiple formations and brands in order to recruit Syrians.
Aymenn Jawad Al-Tamimi is a research fellow at Middle East Forum's Jihad Intel project.