Moroni was chief commander of the Nephite armies from around 74 BC until his retirement, not long before his death in 56 BC. Moroni was able to surround himself with associates of the highest character and professionalism—people like Helaman, leader of the stripling warriors, and Lehi, another excellent field general. Early in his command, Moroni battled against the Lamanite forces by dividing his army into two parts, one under his command and the other under Lehi, and then concealing them in order to surprise the advancing enemy. As the Lamanites under their leader Zerahemnah began to cross the river Sidon, Lehi and his army fell upon them from the rear. A fierce battle ensued in which the Lamanites were forced to flee across the river from east to west. Lehi held firm on the east shore of the river while Moroni’s army came upon the Lamanites on the western shore. Initially, the Lamanites rejected Moroni’s offer to spare them if they would covenant to lay down their arms and desist their warfare, so another battle resulted. In the end, Zerahemnah agreed to a covenant of peace; the Lamanites gave up their arms and returned to their land, sealing the victory of the Nephites under Moroni and Lehi. When they attacked the city, with its reinforced defenses, they were driven back with the loss of all their captains and fled to their homeland. In a subsequent encounter around 64 BC, Lehi and his forces assisted in the defeat of the Lamanites near Bountiful.
That same year, Lehi was placed in charge of the city of Mulek, one of the chief cities of the Lamanites in the land of Nephi. “And Moroni went to the city of Mulek with Lehi, and took command of the city and gave it unto Lehi. Now behold, this Lehi was a man who had been with Moroni in the more part of all his battles; and he was a man like unto Moroni, and they rejoiced in each other’s safety; yea, they were beloved by each other, and also beloved by all the people of Nephi”. Following the insurrection in Zarahemla in which the governor Pahoran was forced to flee, Moroni left Lehi and Teancum in charge of the forces in the field in the year 61 BC and returned to reclaim the capital on behalf of the people. Later, the Nephite generals were victorious over the Lamanites in the land of Moroni, thus restoring peace around 60 BC and enabling Moroni to retire and appoint his son, Moronihah, as his successor. Lehi later assisted Moronihah in defeating the Lamanite armies in Zarahemla.