I'm fairly new to the game so I might not be aware of some rule or other.. but I experienced attacking a wild of level 3 (had only conquered level 1 before) and getting a report that I was victorious - then not actually getting the wild. My troops went home straight away and the square has no flag of mine on it. I have not been presented with any info telling me that I couldn't conquer wilds of a certain level or some other reason for it not to work. Also, my troops died which is really irritating if I'm not supposed to be able to attack them. I tried the same wild again and also a level 2 wild, both with the same result.