Joshua arose up early in the morning, and mustered the people, and went up, he and the elders of Israel, before the people to Ai.
In this connection, we begin to get a glimpse of what kind of book Joshua really is.  It is not a detailed record of everything that happened in the conquest.  The events narrated are given for specific reasons, the religious meaning of each one being the principal reason for its inclusion. We became familiar with this characteristic of the Hebrew Bible in the Book of Numbers especially, where the history of an entire forty years for a whole nation covers only a few pages.