The lore for this is complicated, but follows on from my previous 3 mega builds. The defending force here, occupying the motorway and bunkers, is the corporation Reset engineering, who you will recognise from 'privateers'. Reset has a problem on their hands - they are currently defending their peninsula on which Vivrostron is built on, against wave after wave of 'biotons'
Biotons are nasty creatures - half mechanical, half flesh and muscle, designed to attack enemy forces on sight. They feature many different kinds of weaponry attached to their sides, and come in flying or walking forms.
The biotons were created by the scavenger faction, as a way to properly get revenge on the corporations that are now inhabiting the planet they used to live on. They are produced in 'hives' and attack together in swarms, wave after wave of seemingly endless foes. Only recently have they developed the ability to fly over bodies of water - and Reset is now being cornered. The border wall protects them from the mainland, but their sides are exposed. If they aren't able to hold the biotons back, they will swarm into Vivrostron and destroy the city.