if you have a "The ground is shaking" attack, then you will get multiple Trolls come at your base. if you have wood fence it will stop them for maybe their first swing at it. after that they will bust through easily and then move onto your house. if you have anything against the wall inside your home and they hit the wall of your house, their splash damage will go through and smash your closest items.

I usually do a trench then wood walls, but figured at some point the dev's will fix this so i've gone with a 3 thick Stone wall around my base to see if that can withstand the blows from the Trolls. also don't forget now, that the Furlings and the Berserkers will be inc. next to your base once you defeat last boss.

The key is "doors" all mobs seems to go for doors first not specifically walls. so your door placement and how many you have is key. I only have 1 door on my outside wall now, and anytime my base gets attacked they go straight for that. so i know right off the bat where to go when i see the message of i'm being attacked.