Oh My Papa

Oh My Papa is a side quest in Fallout: New Vegas.

Synopsis
The Great Khans have recently aligned themselves with Caesar's Legion, spelling doom for themselves. This alliance must be broken to both save the tribe and the denizens of the Mojave.

Assassination

 * 1) Speak to Colonel Moore at Hoover Dam.
 * 2) Speak to Papa Khan, Regis and Karl to investigate the rumors of the Khan-Legion alliance.
 * 3) Return to Colonel Moore with confirmation of the alliance.
 * 4) Assassinate Papa Khan and return to Colonel Moore.

Diplomacy

 * 1) Go to Red Rock Canyon and convince Papa Khan's advisers to speak out against the alliance.
 * 2) Regis already was wary of the alliance and does not need further convincing.
 * 3) Jack or Diane at the Red Rock drug lab can be convinced and the other will follow suit. Jack can be convinced with a Speech check of 60, and Diane can be convinced by completing Aba Daba Honeymoon.
 * 4) Melissa at the Great Khan encampment will speak out against Papa Khan after she is told that women cannot serve in the Legion and the best she can be is an officer's wife.
 * 5) Out Karl and his ulterior motives.
 * 6) Find Karl's journal in the footlocker in his room in the Great Khan longhouse, or find his Legion slave ledger in Caesar's tent at The Fort. Present either to Regis.
 * 7) Alternatively, a Speech check of 75 will provoke Karl to reveal his true feelings about the Khans. If this is done in the longhouse, the Khans inside will kill him.
 * 8) Convince Papa Khan to sever the alliance.
 * 9) Pass one of two Speech checks of 75; urging them to claim their glory will cause the Great Khans to flee the Mojave during the Second Battle of Hoover Dam, while urging them to be martyrs will prompt them to perform a suicide attack on the Legion during the battle.
 * 10) Failing the Speech checks, go to the Old Mormon Fort in Freeside at speak to Julie Farkas about the Great Khans. She will direct the Courier to Ezekiel at the 188 Trading Post, who will give the Courier Pretty Pretty Horsies: A History of the Mongol Empire. Presenting this book to Papa Kahn will convince him to either flee the Mojave if a kind dialogue option is chosen, or convince him to head a suicide attack at Hoover Dam if a more unsavory dialogue option is chosen.

Behind the scenes
The title of the quest is a cultural reference to the song "O mein Papa", sung by Eddie Calvert in 1953.

Bugs

 * If you trigger the dialogue where Papa refuses to break the alliance with the Legion before this quest is started, the option will not come back, as it seems to be a one time dialogue option This locks the quest and is unable to be completed.
 * The console command will bring back all of the dialogue options needed to trigger Regis although some of them may still be "grayed out" cycling through all of them normally will allow the encounter with Regis outside of the longhouse.
 * A marker is not placed at Caesar's tent to get evidence for Regis, nor does obtaining Karl's journal complete the objective.
 * Stealing Karl's Journal from his footlocker and then killing him will disable you from using it as evidence against the Legion for Regis, making the slave ledger in Caesar's tent the only usable proof you can use.
 * If you use Speech checks to get Karl to reveal his true feelings about the Khans, resulting in his death, "For the Republic, Part 2" will update to inform you that you've killed the Khans even though none are dead. This will likewise happen if you convince Papa Khan not to side with the Legion while Karl is still in their good graces, as they will again kill him. To avoid this bug, steal Karl's journal (it's in the footlocker in the furthest room from the table) and show it to Papa Khan. Karl will die, but the quest will proceed as normal.
 * If Julie Farkas somehow ends up dead, the quest will be impossible to complete via the book, even if you head to Trading Post 188 and kill Ezekiel for the book. The only way around this is to convince Papa via the speech option.
 * Offering to find proof of female enslavement for Diane will override Regis' quest target, so completing it will also meet his requirement. Convincing Jack through Speech afterward will get all three characters' support, making the trip to Cottonwood Cove unnecessary.
 * If the player convinces Papa Khan to break the Great Khan's allegiance to the Legion, random non-player character chatter after completing the quest will still talk about how the Great Khans were "destroyed" and "massacred," even though a peaceful solution was found.
 * You may get the dialogue option to show Regis Karl's journal as evidence without actually finding it first.