נחמיה, פרק ד׳, פסוק י״ג

Once the enemy retreated and the immediate fear subsided, the builders returned to their posts. At this point, Nehemiah addresses the leadership and the people to explain the logistical and security reality they now face [מלבי״ם]. The construction of the wall is a massive undertaking [רש״י], spread across a vast area and spanning multiple locations [מצודת דוד, שטיינזלץ].

Because of the project's enormous scope, the workers cannot remain clustered in a single area; if they did, the wall would never be completed. Instead, they are forced to scatter [מצודת ציון], with each worker returning to the specific section of the wall he is assigned to build [מלבי״ם].

The direct consequence of this wide distribution is that the builders are separated by significant distances. They are stationed so far apart that a worker can neither see his fellow builder nor hear his voice [מצודת דוד]. This creates a state of isolation, leaving the workers completely unaware of what is happening in other sections of the wall [שטיינזלץ]. To overcome this dangerous disconnect, it becomes absolutely necessary to establish a warning and gathering system, such as blowing a ram's horn, to bridge the physical distance between the scattered crews [מלבי״ם].