Eureka!

 is a quest in Fallout: New Vegas.

Quick walkthrough
take over the hoover dam with the NCR

After saving/ not saving the President, you are asked to talk to the General and given the chance to turn back as this is the begins the final and ending quest for the game. If you say yes, Legion members attack the Hoover Dam and you fight your way through the power plant rooms and head towards their base east. After fighting multiple difficult groups of enemies you are aided by other NCR Rangers. In the camp you fight Caesar's Legate, a very powerful champion of sorts that can be spoken out of fighting if your speech level is over 75. Once defeated, you meet up with the General and everything is a victory. After the speech, the ending game scene then plays out.