Syrian Arab Army soldiers wandering around the massive, sophisticated “underground city” that Jaiysh al-Islam rebels built underneath Douma/East Ghouta pocket in north eastern Damascus
Jaiysh al-Islam was formerly a part of the Free Syrian Army until it disbanded from the FSA in 2013, First known as Liwa al-Islam until their merger with 50 other rebel groups to form Jaiysh al-Islam later in 2013. Their intended goal was *wait for it* the defeat of Assad and the establishment of an islamic state under Sharia law. They were the dominant force of power in Ghouta pocket until their surrender and subsequent negotiated green bus transfer to Turkish backed FSA territory in northern Syria. At the time of transfer, it was counted that 13,000 fighters and their families were part of the bus transfer.
To weather the aerial bombardment by the Syrian air force and the Russian air force, it appears they built this reinforced air raid bunker that eventually grew to become a network of tunnels for the over 10,000 rebels and family members to reside within, when not seizing civilian homes to hide from loyalist observation.
Also, a reminder, Jaiysh al-Islam were the same guys who put hundreds of alawite minority group civilian into 100 cages as mobile human shields
Douma was the site of the recent alleged gas attack that lead to the United States run coalition airstrike on Syrian loyalist targets.