Commentators struggle to grasp what might be meant by the space behind the wall,
let alone its lowest parts
and even the open places.
Nehemiah’s first readers, of course, understood the sentence since they had seen it with their own eyes. For us it is perhaps sufficient to realize that Nehemiah responded to the threats by reorganizing the work crews so that they were ready if an attack materialized (see also Nehemiah 4:16–20). Presumably the reorganization was intentionally visible to observers so that this development would come to the ears of the enemies (and the advantage of a surprise attack be denied them).
13 So in the lowest parts of the space behind the wall, in open places, I stationed the people by their clans, with their swords, their spears, and their bows.