Okay, so Ba Sing Se is an impenetrable city, one that houses many wealth, important families, including the Earth King. Chin the Conqueror decided to face the Avatar rather than take on the city and it's walls. However, as shown in "The Awakening", and as stated in "Avatar Extras", it takes only 5 Earthbenders to bring down the walls. So, how exactly is this impenetrable? Chin would have had many, many Earthbenders in his Army, and it would have been terribly easy to tear down the walls with all of them, so why does he go for Kyoshi, who's power would've been much greater (as shown when she made a new island without so much as breaking a sweat!), had Chin brought down the walls, there probably would've been a different outcome, and instead of Kuei, we would've had Chin IV ruling the Earth Kingdom. I do not see how Ba Sing Se's Walls are so impenetrable with this "little" oversight, do you? Is there a simple explanation that I am missing?