Ha-ha wall
See also the 'Punic ditch'. I can't find a good description online ([1] is the most specific), but basically it's a fortification comprising a human-scale haha with the wall on the outward side, and the slope on the inward side. The idea is that attackers can cross it easily, by jumping down the wall, then charging up the slope, at which point you open fire on them, then when they turn to run way, they have to climb up the wall to escape, at which point they are sitting ducks.These ditches are called Punic not because they were invented by the Carthaginians (Punic is the adjective for things from Carthage, don't ask me why), but because they were incredibly brutal, and Rome's early wars with Carthage were so horrific, they became a byword for anything eye-wateringly cruel like this.[1] https://luntfort.wordpress.com/2012/11/28/punic-ditches/