Mosiah 10:6 - 10:10

Mosiah 10:6 And it came to pass that king Laman died, and his son began to reign in his stead. And he began to stir his people up in rebellion against my people; therefore they began to prepare for war, and to come up to battle against my people.

About this time king Laman died and his fire brand son came to the thrown. He wanted to start a war with the Nephites and started preparations to do so.
[It would be interesting to know why the Lamanites under king Laman did not go to war again even after their defeat in that one battle. Anyway they seemed to have stomach to go to war after just 22 years. Maybe the son was in that battle and wanted revenge now that he was in power.]

Mosiah 10:7 But I had sent my spies out round about the land of Shemlon, that I might discover their preparations, that I might guard against them, that they might not come upon my people and destroy them.

However, Zeniff had spies watching closely the Lamanite to see what they were doing. He wanted to not be caught by surprise again.
[I’m sure that the Nephites knew it would only be a manner of time before the Lamanites tried to come against them again. One then would wonder, if you lived in a neighborhood where people hated you and were look constantly for a way to kill you, why you would stick around? Why would you not want to live where people were loved you and like you being in their neighborhood? Why didn’t these people just give up and return to Zarahemla to where they would not be in danger for those who wanted to destroy them?]

Mosiah 10:8 And it came to pass that they came up upon the north of the land of Shilom, with their numerous hosts, men armed with bows, and with arrows, and with swords, and with cimeters, and with stones, and with slings; and they had their heads shaved that they were naked; and they were girded with a leathern girdle about their loins.

The Lamanites came at them from the north of the land of Shilom. They had a large army and well armed. They had shaved their head and wore only a leather loin cloth.

Mosiah 10:9 And it came to pass that I caused that the women and children of my people should be hid in the wilderness; and I also caused that all my old men that could bear arms, and also all my young men that were able to bear arms, should gather themselves together to go to battle against the Lamanites; and I did place them in their ranks, every man according to his age.

King Zeniff knowing of their coming hid the women and children in the wilderness. He caused all the able bodied men to bare arms which included both young and old. They were then placed in order of age.

Mosiah 10:10 And it came to pass that we did go up to battle against the Lamanites; and I, even I, in my old age, did go up to battle against the Lamanites. And it came to pass that we did go up in the strength of the Lord to battle.

Zeniff, am old man by now, lead his men against the Lamanites. They also had the support of the Lord in the battle.