In keeping with the Book of Mormon's motif of frequent mass migrations, the wealthy Zoramites cleverly figure out who all of Alma's followers are and then kick them out of the country. The believers flee to Jershon, where the Anti-Nephi-Lehi-People-of-Ammon have set up shop. Both groups of people are devotees to the One True Religion, and they get along famously.
Unfortunately, the leader of the Zoramites is a vindictive grudge-holder and he orders the People of Ammon to turn away all the refugees. The People of Ammon have no intention of abandoning their brethren in the faith, however, and ignore the Zoramite leader's request. He, in turn, declares war.
So then the entire Ammonite population relocates to a place called Melek so that the land of Jershon can be used as a designated battleground for the impending showdown between the Nephites and the new Zoramite/Lamanite alliance.
Let's not forget that the Book of Mosiah was full of various groups of people sneaking off, moving around, joining other groups and moving again. I think this plot device has run its course.
This is what you get when you stick your nose into other people's business: all-out war.
Okay, maybe not, but this whole story reads like a cautionary tale about overreaching foreign policy and insensitivity toward other cultures. Alma and his friends waltz in like they own the place, teach a different religion, upset the socioeconomic status quo (although, in their defense, it was an unfair one) and disrupt the Zoramite society to the point that people get kicked out of their homes. Then, people who weren't even involved in the first place are also forced to abandon their homes as Alma's countrymen prepare for war against the Zoramites, who've roped in another initially uninvolved society to help.
And what have we learned from this by verse 14?
And Alma, and Ammon, and their brethren, and also the two sons of Alma returned to the land of Zarahemla, after having been instruments in the hands of God of bringing many of the Zoramites to repentance...
...and as many as were brought to repentance were driven out of their land; but they have lands for their inheritance in the land of Jershon, and they have taken up arms to defend themselves, and their wives, and children, and their lands.