Peace does not come to the Nephites through idle good luck. Benjamin has had to fight with the strength of his own arm, with the sword of Laban (WoM 1:13) in defending his people. More importantly, Benjamin had cleansed the inner vessel by teaching the people and calling them to repentance. He did this with the help of many assistants, and they did speak the word of God with power and with authority; and they did use much sharpness because of the stiffneckedness of the people (WoM 1:17). Certainly, the peace that followed Benjamin's military successes was more a product of his spiritual leadership that his military bravado. In the Nephite world, the only thing which keeps the Lamanites from attacking is righteous living. Had Benjamin relied only on the strength of his own arm, without calling the people to repentance, then he would have fought the Lamanites all the remainder of his days.
'Therefore, if it were possible that you could have just men to be your kings, who would establish the laws of God, and judge this people according to his commandments, yea, if ye could have men for your kings who would do even as my father Benjamin did for this people—I say unto you, if this could always be the case then it would be expedient that ye should always have kings to rule over you' (Mosiah 29:13).