Search and Destroy (Far Harbor)

Search and Destroy is a quest in the Fallout 4 add-on Far Harbor.

Detailed walkthrough
This quest doesn't really offer any advantages, and results in the deaths of everyone in Acadia.

After speaking with DiMA at Acadia one has the option of beginning this quest by traveling to the Prydwen in the Commonwealth and speaking with Lancer Captain Kells. Kells says that the Brotherhood, after some time, has decided to deal with Acadia, and they have sent Knight-Captain Larsen with a small team of soldiers to help wipe out DiMA's community.

Return to Acadia and watch Larsen and his team wipe out the synths (or lend a hand).

If one has not yet completed the main Far Harbor quest line, they will now be unable to do so, and there will be no peace between the residents of Far Harbor and the Children of Atom.

Behind the scenes
Search and destroy refers to a real world military strategy of the same name, utilized in the Malayan Emergency and Vietnam War.

Bugs
If one has completed Close to Home before starting this quest Kasumi Nakano may be seen walking away from Acadia as the player character goes to begin eliminating the synths. Kasumi will be marked as one of Acadia's synths but she is impossible to kill. This can be circumvented by waiting until she has left Far Harbor to begin the attack on Acadia.