Bactria in the days of Alexander was located in the northwestern portion of what is now Afghanistan and Tajikistan. It was bounded by the Hindu Kush mountain range, in the south, and by the Oxus River (Amu Darya), in the north.
Iactria, was a province of the Persian Empire and was conquered by Alexander the Great.
After Alexander, his general Selucus ruled Bactria. It taken from the Greeks, two centuries after Alexander the Great, by the Tokharians.
Bactria is thought to have been the home of Zoroaster.
Selucus had relations with Magadha rulers.
Bactrian Greeks embraced Buddhism and propagated it in China.