‘ And the armed men went before the priests who blew the trumpets, and the rearward went after the Ark, blowing with the trumpets as they went.'
YHWH's instructions were followed obediently. The armed men led, followed by the Ark and the priests blowing the rams' horns, followed by the people, until the city was surrounded. The watchers on the walls waited apprehensively for what would come next.
In the last phrase ‘the priests' is, as shown, not there in the Hebrew. It is to be assumed. The point is that while it was the priests who blew the rams' horns all were seen as participating. This emphasises the importance of the action. The sevenfold horns were depicting the power of YHWH about to be revealed.