I wrote this from memory and used a guide I found that didn't really explain it to well, I will put that in here as well.
Guide i used: http://game-maps.com/W2/Wasteland-2-Topekan-Atchison-Co....asp
Boy this one is a pain in the ass. There is so much that can go wrong. I would recommend using saves/quicksaves often. Also make sure you do not steal the rail spike or the brake shoe.
First thing you need to make sure is that you have decent Brute Force
- 4 should give you a 70% which is enough. If you have Angie with you I think she starts with 4 or 5. EDIT: Thanks to Topherion, You do not need Brute Force, you can apparently use the shovel to dig the totem and have it fall.
Second you will need Surgeon
around 3 or 4. Rose from the Ag Center is fine.
Third you will need good demolitions. I got a follower by doing a side mission, it triggered when I went to an area south west of the Ranger Citadel, should get a call about a mine needing help. Help them out and you can talk to a guy, you saved his mother, and he will offer his services. Other than that you should have Demolition
Fourth you will need Kiss Ass
at 6 and Smart Ass
at 6 (One of these is 5, i forget which, pretty sure it is Kiss Ass, sorry)
Ok, now for the steps:
1. Enter the Rail Nomads Camp
2. Walking forward, someone will be asking for help, follow her and then cross the bridge of shipping containers in the water until you see a person drowning, use Brute Force
on the smaller one (Save/Quicksave before if you are not sure you can get it in one or two tries). Once it falls it will save him and he will run off. Or just use the shovel! Thanks Topherion
3. Walk towards the camp and you will see a person bleeding on the ground. Use your surgeon
on him to save him (Use save/quicksave if you want before attempting, not sure if it can even fail)
4. He will ask you to tell the Chief about him.
5. Somewhere around the entrance to the camp is an offshoot, it may actually be right across from the bleeding guy, i think there is a sign that says "Forest." Find the bike and disarm
the bomb (Save/quicksave before if you want).
6. Go into the second "House" on the right after entering the camp, talk to the people in there until they ask if you would take Ralphy (boy you saved in the water) and say yes.
7. Return to the bike that you diffused and Ralphy will leave your party momentarily while he talks to a girl (Jessie). When she sees the disarmed bomb she will run away and Ralphy will rejoin.
8. Go to the meeting hall (Follow the outer path around passed Ralphys house). It will be in the big building with the train engine out front.
9. Talk to the chief and tell him about the man you saved in the path, ask about the other tribe (Atchisons) and the rail thieves and offer to help rid him of the rail thieves.
10. Head out to the Atchisons Camp and kill the four groups of Rail Thieves until you get a log book update telling you that they are all dead.
11. Go back to the chief and tell him you have rid the area of thieves, then ask him about Jessie who is locked up. (not sure how much more you can do)
12. Go back to the Atchisons Camp and find the large hut where Casey James is.
13. Tell him about Jessie and say you can get her back if he ends the war. Then tell him about the bomb on the bike, he will say he is ready to bargain with the Topekans.
14. Go back to the Topekan chief and ask to have Jessie released into your custody.
15. Go to Casey James and he will be happy to have Jessie back. Ask him for peace or end the war, and you should start getting Kiss Ass and Smart Ass
options. You want to make sure you say to use the Rail Spike as the final spike driven into the rail as a sign of peace.
16. Go back to the Topekan chief, tell him the deal and he will refuse at first but you can get him to agree by mentioning his one arm and he will want Casey to chop one of his arms off.
17. Meet at the entrance to the Atchison camp and talk to Casey. If you have done everything correctly he will agree to chop his arm off.
18. The Topekans will show up, talk to the chief and it should be good, the spike will be driven in and it will be peace at last.
Again, I am sorry this was written completely from memory the day after I got this achievement. Please save before each step in case I missed something or wrote it out of order. Also please comment if you have any issues and I will try to help.