So I just had an interesting and surprising experience. I was dungeoning for a quest (in Medford Hospital) and got a notice "Sanctuary Hills is Under Attack!" Since that's kind of my home base (more space so I built more than the Castle) I went running there to help. I'd hate it if ol' mama Murphy or the
were to get skewered by some raiders. I went on foot since it eats up less in-game time than fast travelling and I was out of verti-bird signal flares. I got there just in time to find the place being attacked by Gunners. I killed the first small group right at the gate since they hadn't made it into town yet, and then heard gunfire further in so I went to investigate. Every one of my little machine gun turrets were running wide open, one settler ran over and hit the switch on the alarm tower I set up, and I saw another settler go running toward the gunners in a suit of MY power armor I had left hanging on the rack. I got to deliver the final shot on like one of a group of a dozen gunners before my settlers and machine gun turrets mowed them all down, lol. I've got 18 settlers so far in Sanctuary Hills, a half a dozen or so heavy machine gun turrets and one artillery cannon. After it was all said and done, the settler in my power armor went over and hit the switch to kill the alarm and everybody went on about their business.
I just thought it was kind of cool to watch one of my settlements take care of themselves like that. I guess from now on if Sanctuary Hills falls under attack, I don't have to worry about coming back to a pile of rubble if I don't drop what I'm doing and run straight there,