What was retained of the book of Mosiah begins with king Benjamin enjoying a time of peace. The context of his speech requires the history of the contentions that had recently ended, else we might not fully understand why he gave that discourse. Verse 12 notes that king Benjamin “had somewhat of contentions among his own people.” Contentions are internal, and wars external. We don’t get the specifics, but understanding the nature of the confluence of the Nephites with the people of Zarahemla, we can reasonably understand that the contentions arose over issues surrounding that merger, and probably the different politico-religious beliefs that accompanied it. In the ancient world, there was not significant difference between religion and politics, hence those two elements would have been combined in the contention.
After the internal contentions, king Benjamin had to contend with Lamanite armies. Verse 13 declares that he wielded the sword of Laban. It is highly likely that this was a symbolic gesture since the sword was over four hundred years old and a sacred relic. It would not have seen actual combat. The intent of the war was the expulsion of the invading Lamanites.