The Jaredites had been fighting vicious wars for years. Yet, they seem to have developed rather structured rules of warfare. Such structure amidst the violence and chaos of war would be surprising if it were not so common among armies throughout history. In this verse, we see that the armies camp next to each other without a midnight attack. Such an attack may well have been devastating but was apparently “against the rules.”
Hugh Nibley
“…in true epic ‘a dignified and fastidious tone’ prevails in the dealings of these men with each other, and strict rules of chivalry are observed, especially in war and duels. So we are told in Ether how Shiz and Coriantumr pitch formal camps and ‘invite’ each other’s armies forth to combat by regulated trumpet blasts (Ether 14:28), exchange letters in an attempt to avoid needless bloodshed (Ether 15:4-5, 18), and rest at night without attempting to attack each other, fighting only at the proper and agreed times (Ether 15:8, 21-26). As in all epics, including Ether, ’the waging of war is not incidental but essential to the heroic way of life.‘ A great chief gains ’power over all the land‘ only after he has ’gained power over many cities,‘ and ’burned many cities,’ (Ether 14:17) in the best Homeric fashion.” (Lehi in the Desert and The World of the Jaredites, p. 409)