"When the first bomb dropped, there was atonement. When the second bomb dropped, there was a reckoning. When the third bomb dropped there was a force so violent that it cracked our Earth in two and divided humanity right down the middle." The Preacher
It is commonly believed that three nuclear bombs devastated Old Earth. Details surrounding the fall of Old Earth are limited and potentially redacted by the Universal Council.
The wasteland surrounding Tier City is now considered a dangerous and restricted radiation zone.