Operation Ticonderoga

Operation Ticonderoga is a Railroad side quest in Fallout 4.

Detailed walkthrough
Upon entering the Railroad HQ the Sole Survivor will be approached by Drummer Boy and notified that Desdemona wishes to speak to them. During the conversation with Desdemona the Sole Survivor will be told to check on the status of the Ticonderoga Safehouse and kill any Coursers that get in their way.

Head to the safehouse, there will be multiple Synths and a Courser named X9-27 who will approach the Sole Survivor, during dialogue there will be two persuasion options, one option asking why the Courser is there and the other stating that the Sole Survivor is from SRB. (This will prompt the Courser to tell the Sole Survivor to leave via the stairs as the elevator is now disabled).

Upon attacking the Courser all Synths will become hostile towards the Sole Survivor, when all enemies have been dispatched head towards the elevator a few levels below. When the Sole Survivor reaches the ground floor they will be attacked by another Courser who is accompanied by a few Synths, once dealt with head back to Desdemona and notify her that all Railroad Agents are dead and the Sole Survivor will be rewarded for dealing with the Coursers.

Bugs

 * When entering Ticonderoga interior cell, Courser dialogue starts automatically. By not talking to him, the game will not allow you to progress even after all targets are dead. This can be fixed by entering the following in console:"setstage RR301 400".
 * If you quickly activate the elevator to head back down, the elevator will stop functioning and lock you out of the building and stop you from being able to complete the quest
 * Resolving the dialog with the Courser peacefully causes all the NPCs in the area to be non-hostile except for the machine gun turrets which will shoot on sight and cause all the NPCs to become hostile. It is possible to either stealth past all three turrets (including one at the entrance by the second Courser) or to stealth destroy them and wait out any Caution, then the synths and Courser will be friendly.