Forgive me as maybe this has already been established as fact - but for all those including myself that were not having their settlements attacked, er, like ever..... Here's why !

I think on another topic about this some other clever dude I think had cracked it, I'm here to confirm he was right.

The Defences work as a deterrent to bands of Maurading bandits or super mutants. If your base has a higher defence than food or water count, you will not be attacked. This, as I was to discover is true!

I've recently set up a new settlement at that Co-op settlement place - not thinking I started planting crap loads of food without building defences or many walls for that matter.... Within the 24hr period, maybe longer I don't know (as I fast travelled back to my Red Rocket settlement to grab some guns and clothing to give to my noob settlers)........
Well, before much longer a pack of super mutants attacks my camp. I wasn't ready..... They killed me first! It was great! I had NEVER seen anything or anyone attack my base before.

Just thought I'd share if any other folk have put way more hours into there settlements than me and have been thinking it was perhaps a bug....

Some things in this game are not really explained......

As it should be. Figuring things out is at least half the fun (for me anyway). This constitutes a spoiler, I would think.

I'm not sure this is 100% of the picture, as I've had plenty of settlements with defenses exceeding food or water, and they have been attacked. In fact, I've had a settlement with a 25 defense and only something like 10 water (or something), and it was attacked.

What I read the other day is that it's food PLUS water (and potentially electricity on top of that as well).

If in doubt, build more defenses, apparently.

With regard to exploration, then yes.....

But systems that govern settlements could have been explained, like Preston could of said "watch out, before you start planting loads of crops gets some defences in place, or waste lander scum will get wind of it, and come down to raid your food supplies!"

It's based on population, food and water count versus the defense stat.. With a higher defense stat, you are less likely to be attacked. It does not prevent attacks though.

Location plays a part, more dangerous parts of the map have resulted in more attacks on my settlements.

Roaming random mobs can still attack.

Supply lines can lure all kinds of [censored] to your settlements.

Spawn locations near settlements can also attack.

You can still get hit with raiders/super mutants/ghouls even when your defense stat is superior..

Yes but that's the first I've seen a settlement get attacked and the main difference to my one in Sanctuary was a lot of food but with no defence and then suddenly - I get raided....

I definitely have had settlements attacked in that scenario...
However, I do not believe sanctuary has been attacked since I beefed it to 160 some defense...sorta disappointing spend all that defense and can't show it off...

Even then it's useless, since the game just spawns all the enemies in the middle of your base, so they can butt**** everyone

Not true, I have 108 defense at Red Rocket and after just putting in a few water pumps (no settlers or crops), super mutants attacked several times.

Ok I thought the indicator of the possibility of a settlement being likely to be attacked was if when you look at your settlement data on the Pip Boy it had a warning sign next to the defense rating. Is that not correct?

I've never had anyone spawn in camp. They can spawn anywhere outside of camp and will go where ever they can find a pathway, so you need to account for that.

I think it means it is lacking essential stuff to fit the needs of settlers...like too little food or water

I was planning on building my settlement on top of an inaccessible fly-over,

though I suspect that will actually count for nothing

Image is a spoiler for the location name:

https://dl.dropboxusercontent.com/u/87106516/overpass.png

It's actually stated in the settlement construction that if your resources (food/water) are over your defense number that the possibility of attacks increases, by how much isn't exactly known. I've had food and water (added together) double my defense rating and I've only been attacked once in sanctuary, though I think this is more because sanctuary is kinda nestled up in the corner and 'out of the way' so to speak.

I will admit that during the one attack on sanctuary I happened to be there and the raiders spawned on the road leading to the bridge.. past the first house on the left (looking at the bridge) which means the choke point I had set up at the bridge was/is kind of pointless.

To me it feels like your character level and/or in game time passing also affects things, I dont do settlements and just use the red rocket truck stop as a custom home and with no settlers, no food, no water etc it seems at first I never get attacked, but as I reach level 20+ I suddenly get the occasional random attack from super mutants when I fast travel there.

I had raiders spawn in the crops of the abernathy settlement inside my fence, some spawn at the back of the culd de sac of the sanctuary settlement inside my fence, supermutants in hangmans alley inside the preset walls, etc... In these cases i had far superior defence. What i did is turn off the rercruitment singal and the attacks slowed down. Dont know f the signal is tied into how often the attcks happen

The recruitment signal does increase the chance of attacks (and why shouldnt it.. you are broadcasting your location to everyone)

Just a thought but I have noticed that non settlement locations that I clear of bad guys and that are then marked as Cleared on the Map later lose the cleared designation.

Is it possible that bad guys move back in and if you don't clear these areas out again, particularly any that are nearby or where part of the initial mission to gain the settlement then the likelihood of your settlement being attacked is greater?

Yes but I have seen it next to the Defense rating so I am assuming that is indicating that you are likely to get attached unless you improve it?

I can concur with that. I have build nothing in settlements because I don't care for it. I have base in Red Rocket as well, with nothing build other than turrets because raids suddenly started happening, first from Super Mutants, and later raiders joined in on the fray as well.

I have it next to most of my settlements and still seems to be random when a settlement gets attacked..I'm really not sure what actually provokes an attack(maybe surplus food/water?)...or what prevents attacks(maybe extra defenses)...I don't really worry much, I got a ton of other things going on...I mostly keep sanctuary, and maybe a couple others, happy and carry on in my travels, ignoring most attacks..

my Sanctuary has 15 people, 24 food, 25 water, and 200 defense (learned my lesson early). I had 1 previous attack before quadrupling defenses. no more after UNTIL I put in the recruitment beacon. I believe that is what is causing the attacks for sure.

But random encounters should happen as is the way in RL.

also, Carla was killed in first attack. her dead body is now a permanent fixture in the street apparently. cannot move her or even select her in build mode. but she still makes for a useful container!

Iv got 30 food 43 water 35 power and 15 settlers now at the castle and a defence of 72 , I occasionally get a single raider pop through my door to meet a man made hall of turret fire , they don't last long .... Also there's a dead naked chic there right in my door , can u move bodies in this game ?

I have had attacks spawn in the middle of settlements many times. Particularly mole rat and radscorpion attacks seems to always spawn in the middle of the settlement or in the middle of a large concentration of crops for me.

That is why I built my main settlement in the Starlight Drive-in completely off the ground supported by wood struts

All your bases are belong to us now. Sorry I couldn't help it. If you're not doing anything with a settlement leave it alone. The only penalty for a raid is broken water pumps and generators but if no ones there you care about they can be unhappy and leave. There are way too many settlers who are way too needy.