The Mission of Alma the YoungerAlma 6:6 around 82 B.C. when Alma the Younger, after having preached in the city of Melek, came upon the city after traveling northwards for three days. After initially being rejected by the people, Alma left the city, but was met by an angel, who instructed him to go back on an especial mission to declare that if the city did not repent, then it would be destroyed. The great urgency of this mission was due to the fact that the people of the city of Ammonihah were plotting to destroy the freedoms of the Nephite people.
Upon returning, Alma met Amulek who became a companion for Alma's mission and a second witness to the truths that he declared.
The city of Ammonihah was known for the wickedness of its lawyers, and it was with these characters that Alma and Amulek had their initial confrontation. The most notable of these was Zeezrom who initially tried to entrap them, but was finally convinced by the testimony of Amulek and brought to repentance.
The people at large, however, were unrepentant. Many righteous people fled the city, or were cast out, while Alma and Amulek were cast into prison. The righteous people who remained were burned, while Alma and Amulek were forced to look on. Finally, after enduring more persecution while in prison, Alma and Amulek were freed by the power of the Lord, which caused the ground to shake and the prison walls to tumble to the ground.
The end result was that the people did not repent and, having cast out or killed all of the righteous, the city was prepared for the prophesied destruction.
In Alma 16:2-3,9-11 the destruction of the city of Ammonihah is described, occurring in about 80 B.C. The destruction of the city of Ammonihah was brought about by the Lamanites, who in a fit of genocidal rage, swiftly fell upon the city and destroyed it, killing every inhabitant within one day. The anger of the Lamanites was inflamed by the conversion of a large group of Lamanites (who came to be known as the Anti-Nephi-Lehis) to the Church of God, which religion was, up until that time, almost exclusively a Nephite religion.