For the Republic, Part 2

 is a quest in Fallout: New Vegas given by Colonel Moore at the Hoover Dam.

Detailed walkthrough
After completing the first two quests, head to the Hoover Dam and talk to Moore. She will have you head to The Great Khans base in Red Rock Canyon. Head into the building with the marker and you will find the leader. Talk to him and you will learn that they have an alliance with Caesar's Legion. Your orders were to kill them if no alliance could be made so go into V.A.T.S. mode and take out as many as you can. They are relatively weak so it will not be that hard. Walk out and fast travel to the dam and report to the Colonel. She will inform you about the Omertas and send you to find out what is up. Talk to the secretary at the NCR Embassy and she will direct you to the Gommorrah's receptionist. From there go talk to Cachino and wait until he walks away. The easiest way now is to crouch, activate a Stealth Boy (Fallout: New Vegas), and pickpocket his journal from him. Confront him about it and find out the information needed. Head to Troike and the talk about Cachino and then lie to him. (This will cause a loss of karma) He talks about thermite and have him put it with the weapons. Exit the casino and re-enter and talk to Cachino. You find out that he got caught and told the bosses your name. Talk Cachino into killing them during the meeting. Follow him and you will be given a sawed-off shotgun. Whichever way suits you, make sure the bosses are dead. The next part of the quest is very challenging. You are required to eliminate the Brotherhood of Steel. I suggest that you complete the quests for the Brotherhood first. When you are ready, head into the bunker and go towards Head Scribe Taggart. If your science is high enough hack the self-destruct computer. If your science is not high enough, you have to pickpocket the keys from the Elder, Head Scribe, and Head Paladin. Trigger the self-destruct and be ready for a fight. If you have enough Stealth boys you can sneak your way out. If not, prepare for a heavy fight against many Paladins, Scribes, and turrets. Whenever you exit the bunker, it explodes and you cannot get back in. Go to Moore to finish the quest.

Bugs

 * If you are working with Yes Man and do You'll Know It When It Happens quest before doing this one and choose to bring a truce between NCR and the Brotherhood it will bug out and you will not be able to complete this quest. When speaking with the Colonel she will ask if the President is safe and you will have no dialogue choices to complete the quest even though you already did it.

If you already killed Chachico, this quest is not completeable.