In Season one of Attack of Titan, everytime titans were about to breach a wall, if I understand correctly, they breached a city located in the edge of the wall first, and through that city, they breached the wall. In episode one of the second season of Attack on Titan, it is said wall Rose was breached but I couldnt hear anything about how they entered. is it known? Did they attack a borderline city first?
The wall hasn't been breached. The titans didn`t came from outside the wall but have been created inside the wall. This should be answered in one of the next episodes and has been shown in the 38. chapter of the manga.