After the murder of Gideon mentioned in the book of Alma and the execution of Nehor, the man who introduced priestcraft to the Nephites, there arose one after the order of Nehor whose name was Amlici. According to Chapter two of the Book of Alma, he was very cunning and wise according to the wisdom of the world (verse one) In verse two, he had gathered a great following of people.
His people endeavored to make him King over the Nephite (Alma 2:3). Now an alarm was set out through out the church established by Alma the elder because of this, knowing that Amlici would deprive them to their rights and privileges and would destroy the church of God if made king (Alma 2:4). But one safeguard was in place that the will of the people had to be behind him to establish him king over the people (Alma 2:3). And when the people assembled to cast their opinion on the matter, the whole debate became contentious between the two camps (Alma 2:5). And the matter was laid before the judges of the land in the various assemblies of the people (Alma 2:6)
The voice of the people came back against Amlici and he was not made king over the Nephites (Alma 2:7). Not content, Amlici stirred up his followers against those who were not in his favor (Alma 2:8). He was consecrated king over his followers and he commanded that they take up their weapons of war against the Nephites to subject them to him. After this time his followers were known as Amlicites. (Alma 2:9-11)
After the division
After the division took place among the Nephites, there unfolded a war between the Amlicites and the Nephites (Alma 2:11). The Nephites were aware of their intentions and prepared for war, building up arms and appointing captains, higher captains and chief captains (Alma 2:12-13).
Amlici prepared the Amlicites in much the same way, building up arms and appointing rulers and leaders of his people. (Alma 2:14) Though, it should be noted that the Book of Mormon's discerning between the two leads to speculation as to the nature of Amilici's army commanders.
The Amlicites came up to the land of Zarahemla over the hill Amnihu which was east of the river Sidon and began to wage war. Alma the younger was the chief commander of the Nephite forces. Though many Nephites died in the battle, the Nephites overcame them due to the strengthening of the Lord and drove them with a great slaughter and pursued for the rest of the day until Alma and his forces could no longer. The Nephites broke camp in the valley of Gideon. (The man who was slain by Nehor.) (Alma 2:15-20)
Afterwards, Alma sent Zeram, Amnor, Manti, and Limher to spy on the remnant of Amlicites so as to understand their plans. To their surprise they reported to Alma that the Amlicites were joined in the land of Minon, above Zarahemla, in the course of the Land of Nephi, came a huge host of Lamanites that the Amlicites joined. They were already making their way back towards Zarahelma. (Alma 2:21-25)
Alma and his armies then left the valley of Gideon and moved across the river Sidon. They then were set upon by the hosts of Lamanites and Amlicites. A great battle ensued and the Nephites with the aid of God drove them back. Alma slew first Amlici and then drove back the king of the Lamanites and cleared the bank of the west side of Sidon and the joint army of Lamanites and Amlicites fleed before the nephites and went of into the wilderness (called Hermounts) out of the borders of Nephite Lands. (Alma 2:26-37)
After the battle, the dead were buried but not numbered due to the greatness of the number that were slain. (Alma 3:1 also see Book of Mormon: Student Manual 121, chapter 22 section 13)
In chapter three, from verses four to eighteen, there is an explanation of how the Amlicites were now cursed with the Lamanites due to their marking themselves, just like God had set a mark upon the Lamanites. The Book of Mormon: Student Manual 121 suggests in chapter 22 section 14 that this may have been done so that the Lamanites could know who was an Amlicite ally and a Nephite.