Alma 2:16 - 2:20
Alma 2:16 Now Alma, being the chief judge and the governor of the people of Nephi, therefore he went up with his people, yea, with his captains, and chief captains, yea, at the head of his armies, against the Amlicites to battle.
The armies of the Nephites were headed by Alma himself on account of his being the head of the government and chief judge. He was in command of all the Nephite armies that went up against Amlici and his army.
Alma 2:17 And they began to slay the Amlicites upon the hill east of Sidon. And the Amlicites did contend with the Nephites with great strength, insomuch that many of the Nephites did fall before the Amlicites.
When the two armies met, the battle was intense. The Amlicites fought with great vigor and it appeared at one point as if they were going to be the victor.
Alma 2:18 Nevertheless the Lord did strengthen the hand of the Nephites, that they slew the Amlicites with great slaughter, that they began to flee before them.
However, the Lord strengthened the Nephites the battle was now going the Nephites’ way. The Amlicites were seeing large numbers of their forces being slaughtered by Alma and his army.
Alma 2:19 And it came to pass that the Nephites did pursue the Amlicites all that day, and did slay them with much slaughter, insomuch that there were slain of the Amlicites twelve thousand five hundred thirty and two souls; and there were slain of the Nephites six thousand five hundred sixty and two souls.
The Amlicites began to give way and run for their lives. The Nephites did purse them all that day so they prevent any of them from escaping. The Amlicites suffered 12,532 dead while the Nephites counted 6,502 dead.
Alma 2:20 And it came to pass that when Alma could pursue the Amlicites no longer he caused that his people should pitch their tents in the valley of Gideon, the valley being called after that Gideon who was slain by the hand of Nehor with the sword; and in this valley the Nephites did pitch their tents for the night.
When night came the Nephites made camp in the valley of Gideon. This valley was named after the Gideon who was killed by Nehor.