A wall to keep the Netherese out and the wealth of the Empire of Cormyr in.
It’s not the first time that trouble has trickled out of the Anauroch Desert to plague the line of Azoun, but now it finds the kingdom of a saddle sore seventy something with plenty of internal strife and court problems to deal with, while the horde to the north seems nearly invincible. Cormyr needs time to heal and grow behind a bulwark. The Bedouin raiders along with the legions of the north still must travel the roads and arteries of the empire to harry the south lands, and trade is more important to the shadows and shades of Netheril than it is to a rich country to the south that is tired of their bellicose bluster of former empire.
“Build a wall” the King says, and the engineers and legions of Purple Dragons have responded. Every criminal who would have faced the noose or labor camps, has been joined into a gang headed north to stack bricks, chisel stone and bend iron into the thick wall, the road to feed its garrison or to build the watchtowers on it.
A few days south of this massive construction, merely a year into the project, Fallcrest, a small town straddling a Forest preserve, stuck in an antique arrangement with the King, without true nobles in charge, grows with the river traffic for both quarried stone, labor and supplies for the soldiers and workers of the northern project. Mules lead barges to the locks, cranes switch back the loads up the locks, and old ruins once merely buried by the local farmers are exhumed for cheap building supplies. Mummy wrappings are rendered and sold once their inhabitants are dealt with. A growing swamp to the north is eyed by settlers and cattle men for draining and use in agriculture.
A wall by itself, is not truly what will defend the empire, but a frontier built to support that wall will fatten men on the wealth earned in building and maintaining that wall, and those men will hire the folk, pay the taxes and eventually lead the day against the Netherese enough to throw trouble in their path. This is how an old king goes to war, knowing that even though he will in all likelihood pass on before the campaign is done, it will be won by men far less tired than he himself is.