It appears that terrorist forces in East Ghouta, to the east of Damascus city center, thought that a simple water-filled trench, effectively a moat, could stop the advancement of the Syrian Army.
Terrorist forces had years to prepare their defenses in East Ghouta, and some of the most commonly found defense infrastructure and the constructed trenches.
With trenches having a width of four meters and filled with water, it was expected that it would severely hinder the movement of tanks and armored vehicles in East Ghouta.
However, a simple military bridge that is quick to assemble and strong enough to allow heavy vehicles to cross the water-filled trenches has proven to not hinder advancing forces at all.
Effectively, the trench system found throughout East Ghouta has been of no use to terrorist defenses.