Diodotos I founded the Baktrian Empire by seceding from the Seleukid Empire in either 255 BCE or 245 BCE. While Diodotos was known in antiquity by both Greeks and Romans, the primary details of him were written in a book that sadly didn’t sell many copies, and was therefore out of print by the time historians wanted to know.
We do know that he was invaded by Arsaces and that either Diodotos won, or the two sat down for some beers and came away allies.
While now Afghanistan isn’t considered an ideal location, back then the area was extremely wealthy and termed “The thousand cities of Baktria.”
Note that this coin still says “Of King Antiochos”, probably because it was minted at a time when independence from the Seleukid Empire was not yet fully broadcast.
Diodotos I, the Seleukid satrap of Baktria, declares independence from the Seleukid Empire, establishing the Greco-Baktrian Kingdom.