When do raiders start attacking your vault?

Question

I'm pretty sure I've never been attacked by raiders until I have a dozen or so vault dwellers, although I haven't tested this properly yet (I normally grow my vaults quite quickly). I'm aware Deathclaws are 'unlocked' at a certain population (60 for regular and 35 for survival vaults) - is there a similar, lower threshold for raider attacks, or are they timed, or does it depend on vault caps, or a certain room, or something else?

Or have I just been lucky? I suppose it's possible, but I assume there's something preventing attacks in e.g. the first 60 seconds of play...

Answer 1

Raiders will come in middle game randomly to surprise the vaults owner to make the player think about preparing for a raider fight.

To stop raiders from killing your people make sure every room has a person with a weapon so the person can kill the raiders more easy then just fist.

A raider will have a stone, scarp sword as a melee so using a fist as a weapon will not be so easy.