I love those Natives! :D Those guys are so destructive against buildings. When the Incan Huaminca is upgraded, he has a Siege Attack of 60! So in the end I'm attacking the enemy Fort with 13 of those guys which causes 780 damage per attack wave. I also put my other units in front to preserve them. I found something interesting in this level regarding the victory dialog skip I'm using. If you put the Heavy Cannon under a group hotkey, the dialog won't be triggered. The only reason I can think of as to why it happens is because then the Heavy Cannon belongs to you, not the Inca's anymore.