Alma Ch55

Although Moroni wants his people back, he refuses to exchange because Ammoron didn't promise to stop the fighting, the Lamanites are then tricked by the oldest trick in the book to set the prisoners free. The Nephites are freed and the city of Gid is taken over without any bloodshed. Moroni fortifies and plans more to get back more cities.
Moroni gets upset at the letter Ammoron (if you didn't read my interpretation it's in the previous chapter) because you can tell Ammoron knows full well that he is leading his people into darkness (v1). So he says, probably to his fellow war council members, "I'm not going to give this creep back the prisoners just so he can try to gain more power, he has to promise not to attack anymore. We know where the prisoners are being kept, lets go get them back ourselves with what they used to do to get people out of bondage from the Lamanites (v2-3)."
So he searches among his people for a convert Lamanite, and found one of the servants of the old murdered king whose name is Laman to lead a group of Lamanite looking men to give alcohol to the guards at the city of Gid, where the Nephite prisoners are kept (v4-8). The guards totally believed that the group were escaped prisoners that had stolen the booze and decided to drink it all that night (v9-13). Now this was specifically prepared to be extra strong, so as they drank they got wasted and passed out, at which point the Nephites came and gave all the prisoners weapons to fight (v14-17).
Moroni did this all while they slept so he didn't have to kill any of them, but if they had woken up they would have died, he actually wanted to save them, or at least give them a chance to surrender, so the army surrounded them (v18-21). When the Lamanites woke up, they were surrounded and completely surrendered their weapons on the spot liberating the Nephite prisoners and becoming prisoners to Moroni who started making them work to fortify the city of Gid (v22-25). After they finished fortifying Gid, they went to Bountiful to work and be a part of the many many other prisoners they had already taken, but they guarded them well and never fell for the silly schemes the Lamanites try to pull (v26-29).
I mean seriously the Nephites JUST pulled the giving alcohol to the guards thing and the Lamanites are trying to poison the guards the same way, so unimaginative (v30). Also the fact that the Nephites are being righteous and being blessed by the Lord for their faith, and by that I mean they are first testing the drinks on Lamanite prisoners (v31-32). It became very necessary for Moroni to start planning to take back the city of Morianton because the Lamanites were using it as a supply for their army, a strong hold, and its the reason the war continues, so they start planning at the end of the 29th year, but we will hear about it later because this chapter is over (v33-35).