3Ne Ch4

Because the Nephites were mindful of the Lord, they are able to win against the Gadianton robbers and the leader, Giddianhi is slain while his successor is hung in the same chapter. Glory is given to the Lord for the Nephite victories.
The Nephites had deserted their lands when they gathered in one place, so the robbers began coming and taking possession but were unable to stay because there was not food for them except in the wilderness or if they tried to attack the gathered people and take their flocks (v1-4). The Nephites were half hoping to starve out the robbers by keeping their food fortified with them being ready to stay that way for 7 years, but it didn't last that long because Giddianhi say it was necessary to attack because they needed subsists other than making it themselves (v5-6). When the robbers came to attack in the 6th month of the year they looked horrific because they covered themselves with blood, and they thought that the Nephites were scared because as they approached, the Nephites fell to the floor to pray (v7-10).
The battle commenced and it was a terrible slaughter, worse than all before, in which the Nephites came out triumphant driving back the robbers and even pursuing them to slay all they could including Giddianhi, their leader (v11-14). The 19th year there was not attack, but in the 20th year, the new leader, Zemnarihah, organized a futile siege upon the gathered Nephites to try and impose their will upon them (v15-18). If you remember the robbers didn't have any provisions because the Nephites were ready in their fortification to last for 7 years, so the robbers only had meat from the wilderness and began to perish as the Nephites were strong and attacked their armies every once in a while (v19-21).
The robbers could tell they were getting nowhere and convinced Zem to give up and head north go get food, but Gidgiddoni knew they were weak and about to retreat so he sent out his armies by night to surround the robbers (v22-26). Many yielded but the rest who did not surrender were slain including Zem who was hung in a tree that was cut down when he was dead (v27-28). I'm sure there is symbolism somewhere in there but I have no idea why they would cut down the tree after he died but it might do with what they said as they did this in v29 about preserving righteousness by causing people who are secretive are felled to the earth.After the defeat of the robbers and the slaying of their leader it was cause for so much happiness among the people and praise to the Lord for granting them deliverance (v30-33).