Crush the White Legs

Crush the White Legs is a main quest in the Fallout: New Vegas add-on, Honest Hearts. The opposite quest is called Flight from Zion, in which the player chooses to help the Sorrows and Dead Horses flee Zion Canyon.

Detailed walkthrough
Tell Daniel that you wish to fight and wipe out the White Legs with Joshua Graham; this will cause Daniel to show signs of anger, and will hastily disagree with your decision. You then appear at the Caterpillar's Mound with Joshua Graham and he will brief you on the situation, explaining that you, he, and a combination of Sorrows and Dead Horses warriors will assault the White Legs encampment at Three Marys.

After talking to Joshua Graham, you will get The Way of the Canaanite follower perk. Fast travel is disabled during this quest, so you have to trek to Three Marys while fighting many White Legs along the way. The White Legs mainly seem to appear in groups of three at predetermined locations.

Follow the river south-west towards The Bend Bridge, continue along the river south-east towards Virgin River, but keep going south. The entrance to Three Marys is just south of the Red Rapids Docks along the river. When you arrive at the entrance to Three Marys, you must fight your way through to the center of the camp. You will need to fight many White Legs, and the further you get inside the camp, the more you will see friendly tribals who will be hunting down and executing fleeing White Legs or helping you finish off the survivors.

When you get to Three Marys' caverns, specifically under the arch, the White Legs will detonate mines from an above rock formation, blocking the direct way to the camp's center (this obstruction will not be cleared, even after the ending). After this brief cut-scene, Joshua will say that you and he will end this no matter what. He will leave, and you will lose his perk.

Go through Three Marys' caverns, fighting more White Legs and you will end up on the other side of the blockade. You will then travel through the innermost parts of the camp. There are many White Legs being hunted at this point, fellow tribals are everywhere and you can make a relatively safe trip to the camp's center.

Once your destination has been reached, you will go to a cut-scene of Joshua Graham executing two White Legs. He will then make a brief declaration to Salt-Upon-Wounds, mentioning the fall of New Canaan, Syracuse and Caesar's Legion. He will also quote the Bible, less now than before and speak in the language of the White Legs.

After this speech, Salt-Upon-Wounds will cry out to you asking for help, claiming you are the only one who will listen to reason. You can then choose to either talk to Joshua or fight Salt-Upon-Wounds. To talk Joshua out of executing Salt-Upon-Wounds, you must pass two high level speech checks. With a Speech level of 75, you can talk Joshua down enough to at least let Salt-Upon-Wounds fight back before he is executed. Passing this speech check but failing the next one will result in Salt-Upon-Wounds and two more White Legs attacking after dialog is exited. With a Speech level of 90, you can talk Joshua out of killing Salt-Upon-Wounds entirely. The ending received will be slightly different than if you pass only one speech check. If the Courier has the Sneering Imperialist perk, he/she can tell Joshua to "Cap General Gobbledigook".

After either killing or sparing Salt-Upon-Wounds, the ending cinematic will play, involving all of the appropriate character choices you made. Despite this being the staying option, Daniel, Joshua Graham, Waking Cloud, Follows-Chalk, and White Bird will not be in Zion anymore. You will still find their clothes and other ending gear (such as Joshua Graham's Scripture) in the final footlocker, just before you enter the southern passage to return to the Mojave Wasteland. The extra unique gear will not be there if you already looted it from their corpse, however.

Bugs

 * If Joshua is too far behind the player when rock detonation occurs, you may be notified that he has left your party and lost his perk, but he will not initiate the dialogue telling you to look for another way around, and when you reach Salt-Upon-Wounds, Joshua will not be there, and you will be unable to move or interact.you can solve this by waiting for Joshua before you enter the area and kill him, it will fail the mission but will activate a new one and you can fast travel and get the map to get out of Zion (you will NOT get any or the items at the end but you will keep your save) or reload a save before Joshua leaves your party. (On PC, there may be another possible workaround. Open console with ` and type tcl to toggle no-clip, then phase around the walls to bypass the point in which the cut-scene would activate. Speak directly to Salt-In-Wounds and agree to talk Joshua down, then pass the Speech checks to resolve the situation peacefully. Doing this will cause the quest to complete and initiate the ending.)
 * If you reload the last autosave where you exited Three Marys' caverns immediately after killing Salt-Upon-Wounds while the end scene music is playing, it will continue to play throughout the battle leading up to the next confrontation with Salt-Upon-Wounds.
 * When traversing the lower path instead of the upper path in the canyon, after a White Legs tribal is assassinated on the top cliff it may turn ragdoll after hitting the ground and injure the player
 * In some cases, if you don't part ways with Waking Cloud before being transferred to Joshua, he will not start dialogue with you, you are stuck and you will have to reload a previous save.