Question about walls and biters

[Flubberj]

So currently I’m running a super low pollution factory and I’ve gone out and killed a few biter nests but I haven’t made any extraordinary efforts to deal with them. I’m transitioning from steam to solar power and currently looking at walls to wall off territory for myself. My question is if I build walls around my base and a group of biters decides to settle near it, will they attack if my pollution cloud never reaches them? I know you can defend them with gun turrets and the like but I’m curious to if I could simply wall off a very large area, slaughter the bugs inside, and then not worry about them until I want to expand past my wall (assuming my pollution cloud never reaches another nest to provoke an attack)

[Loewchen]

Yes, they will attack you without pollution reaching them.

[Jap2.0]

Bugs will only attack you in 4 cases:

• 1. Your pollution cloud reaches them
  2. They attempt to expand into your territory
  3. You go near them
  4. You attack them (including with artillery)

[JimBarracus]

If biters are hit by a pollution cloud they get trigered and try to attack the source (boilers, smelters etc)
When their path is blocked they go into rage mode and attack everything around them.

Your walls need a defense line, sooner or later.
Artillery with some range upgrades can keep biters far enough from your base, so that they are out of reach for pollution clouds. Depending on the terrain.