Alma 50:1

And now it came to pass that Moroni did not stop making preparations for war, or to defend themselves against the Lamanites; for he caused that his armies should commence in the commencement of the twentieth year of the reign of the Judges, that they should commence in digging up heaps of earth round about all the cities, throughout all the land which was possessed by the Nephites;

Moroni did not stop getting ready for war or to protect his people against the Lamanites. He told his armies to start at the beginning of the twentieth year of the judges. They started piling up dirt around all the cities in all the land that the Nephites owned.

Moroni never stopped preparing for war. At the start of the twentieth year of the judges, he set his armies to work digging up huge mounds of earth around every city the Nephites controlled.