If we’re going to be honest with ourselves, it isn’t a necessary account. Truly, if you read Joshua 1 and then begin reading Joshua 3, the account of taking the promised land makes perfect sense. In some ways, the story actually flows better. But the author purposefully interrupts his retelling of the conquest to shoehorn this account into the book. While it’s not essential for retelling history, it’s essential for making his theological point. The author is going out of his way to do more than simply tell history. He has a theological agenda. He wants us to know something about God, and by going out of his way to do so, he makes his point even clearer.