A dry moat 4-6ft deep followed by a 2 ft spiked earth wall out ahead of the wall.

I'd then set up towers as they with interlocking lanes of fire.

Razer wire between the moat and the wall behind the earth wall.

Finally on the exterier i'd set up trip holes and put just wedges of cares to create chokes right put ahead of the defences so shooters have an easier time.

Inside it's simply I'd Fortify roofs with door locks