How To Use Defensive structure In A Sentence

Brick superstructures would no longer do, and it soon became the norm to have double walls with all-stone inner and outer faces, bonded by a rubble fill, with increasingly elaborate defensive structures around the gates.
As the traceried windows suggest, it was less a defensive structure than a six-storey mansion built on a castle theme – truly an Englishman's home. Gothic architecture in Britain: examples from the era
The building seems to guard its secrets, the barred apertures underscoring its function as a defensive structure.
As a defensive structure it would have been continuous, as the river is easily fordable.
Most have developed all kinds of defensive structures that protect the weakened self against further disorganization.

Protesters complain that this defensive structure is an outrage - an infringement on free speech that will only incite a siege mentality.
Either the breach was still defensible with a sufficiently large and determined force, or Chester was not an important defensive structure at the time, or any repair/refortification has not left any evidence. Chester in the seventh century: the fortress defences