Like all units, Wall Breaker choose the nearest “preferred” target – walls. Since you don’t have direct control of any units, nearest is determined by some type of aggro algorithm. Here I am going to share with you some useful Wall Breaker guide. Hope you will like it.

Most players will think the Wall Breakers will just wall in a straight line to the nearest wall, which makes Wall Breaker fairly straightforward. But actually there are some more exotic wall designs, which are clearly designed to “lure” Wall Breaker away from the main defensive walls. When this is done correctly it makes Wall Breakers almost useless，because it would take way too many to clear out the “lure” walls.

Of course We should know more about the characteristics of Wall Breakers to use them better. Firstly, Wall Breakers will look for the nearest buildings that is trapped (fully or partially) by walls. Secondly, they will choose the shortest path towards that building and blow up walls that are in its way. Finally, after the wall is blown up, Wall Breakers will choose the next building that is still trapped by walls, tun straight towards it, and blow up walls that are in their way.

Of course We should know more about the characteristics of Wall Breakers to use them better. Firstly, Wall Breakers will look for the nearest buildings that is trapped (fully or partially) by walls. Secondly, they will choose the shortest path towards that building and blow up walls that are in its way. Finally, after the wall is blown up, Wall Breakers will choose the next building that is still trapped by walls, tun straight towards it, and blow up walls that are in their way.

And we cannot fool Wall Breakers by using spikes or short decoy wall sections. We also can no longer lure Wall Breakers with “vestigial”walls. Wall Breakers will not target single walls. There needs to be at least 3 connected walls for a Wall Breaker to target it, and it must be protecting a building fully or partially.

As added info, I’ve found this video from Flammy extremely informative. He shows the Wall Breaker aggro in action, and even has some crude measurements of aggro distance.