I am trying to get the trophy "get off my lawn" for stopping 50 raider attacks. This is annoying me since I don't seem to have any control over when the raiders attacks. I get plenty of attacks invmy vault but they mostly seem to be deathclaws and not raiders. It seems like raider attacks are the least common type of attack on my vault. What can I do to increase the frequency of raider attacks on my vault?
No, it is not possible to trigger raider attacks. If you progress too far, too quick it might be impossible for you to obtain this troohy. When your vault is small you mostly get attacked by raiders. As it gets bigger this becomes a mix of many. It will get to the point when only deathclaws attack.
I played with this for ages. There is absolutely nothing I could find that influenced the frequency of attacks in general or increased the odds if it being a raider attacks.
My last resort was to downsize my vault. I deleted all rooms I didn't need and compressed it all down so that my vault was 4 levels deep. I evicted most dwellers leaving only 35 of the strongest behind. I ended up not getting any attackers at all after this. All events in the vault seemed to stop completely.