3Ne Ch2

As wickedness grows among the Nephites and Lamanites, the righteous are forced to join and defend themselves against the Gadianton Robbers. All the Lamanites that convert become white and are now called Nephites.
Just 3 years after the signs of Christ's birth the people forget and imagine vain things in their heart because they have let satan take possession of their thoughts and lead them into wickedness (v1-3). This pattern continues for 4 years and the 99th year ends so the Nephites start to reckon their time from when the sign of Christ's birth was instead of since there has been judges making it year 9 now (v4-8). Nephi's father, Nephi, was still never heard from again but the people stayed wicked for 4 more years despite being preached to about repentance (v9-10).
Now in the 13th year since Christ's birth, the Gadianton robbers were so numerous that they pillaged and destroyed many cities causing the Lamanites and Nephites who were still righteous to join to fight against them (v11-12). The wars were bad and threatened utter distruction but they were able to hold strong because the Lamanites joined them, and those Lamanites were blessed by taking away the curse from Laman and Lemuel from them which means they are now true Nephites (v13-16).