The Lamanites “began to prepare for war” (v. 6) suggests that the Nephite civil defense had caused the Lamanites to hold off their efforts to bring the Nephites into bondage (9:10). The death of the Lamanite king (v. 6) may also have been a factor.
The men being placed in their ranks according to age (v. 9) was apparently a Hebrew custom (see 1 Nephi 18:6). The order being from oldest to youngest is suggested by the first mention of the old men being armed. Their going up in the strength of the Lord is also commented on (9:16–19).