Bactria and Margiana, as names, both refer to particular regions in Central Asia, and are both Greek versions of Persian originals. They were used as divisions within the Achaemenid Persian Empire, and subsequently in Alexander's Empire, before then being inherited by the Seleukids afterwards.

The Bactria Margiana Archaeological Complex (catchy, int it) is a Bronze Age complex culture named for the fact that it was primarily discovered in those two regions, and is more commonly known as the Oxus Civilization. We don't know 100% how this culture relates to the later Margiana and Bactria, aside from being located in the same place, as the BMAC didn't, to our current knowledge, possess any written documentation. However, what we do know is that this culture had complex cities, administration, irrigation canals, and trade contacts with surrounding regions and cultures- a trade outpost seemingly related to the Indus Valley Civilization was found in an area of Bactria by accident, when archaeologists were surveying the irrigation network near the site of Ai Khanoum.

These networks of irrigation canals were still in use by the time of the Achaemenids and Alexander, and were highly necessary for life in Bactria and to some extent Margiana- both regions are quite arid outside of oases and rivers, and it was necessary to channel the river waters to enable wider scale crop growing. That Bactria was famously urbanised and fertile at the time of Alexander says a lot about how successful these irrigation efforts were.

Both of these regions are arid, and mountainous. Bactria followed the middle course of the Amu Darya river, known to the Greeks as the Oxus and to the Achaemenids as the Wakshu, and was nestled among the foothills of the Himalayas, controlling key passages between India and Central Asia. Margiana was originally part of Bactria, and when separated from it constituted a region surrounding the city of Merv, an oasis city much like Balkh (ancient Bactra) was in Bactria proper.

Bactria is sometimes identified as the original homeland of Zoroaster, and has strong connections to wider Iranian culture as a whole. Despite that, Bactrians were understood both by the Achaemenid Persians and Greeks as being a distinct people from the Persians, and from others such as the Sogdians who lived very close by. It's in this context that Alexander spent 2 years conquering and pacifying Bactria and the surrounding region during his conquest of the Achaemenid Empire.

Alexander had planted colonies of Macedonians in Bactria, but the Seleukids that inherited the region did so more extensively. Seleukos' (the founder of the Empire) first wife, Apame, was Bactrian, and his successor Antiokhos was the product of that marriage. It's also known that Antiokhos was co-regent with his father for some of the latter part of his dad's reign, and was in particular responsible for the Central Asian satrapies, since they were financially important, and formed a key frontier of the Empire.

Later, however, the governors of Bactria became powerful in their own right, and when the Seleucids were distracted by a civil war the satrap Diodotos declared Bactria an independent kingdom, passed the title onto his son Diodotos II. This son was overthrown by another Greek named Eucratides, who then successfully defended the kingdom against the Seleukids, who under Antiokhos III had finally recovered enough to try to recover their lost eastern territories.

An independent Greek ruled Bactrian kingdom then lasted for about another century, and this gave rise to what we call a distinct Greco-Bactrian culture, combining elements of both and creating something new. Greek style buildings were made using Bactrian techniques, temples used by both Greeks and Bactrians came into existence, Bactrians found their way into the civil service of the kingdom.

The independent Greek-ruled kingdom came to an end with a bang, a big invasion by steppe nomads that saw major cities sacked, though the Greeks themselves remained afterwards. This period is a little fuzzy due to a relative lack of evidence outside Chinese literary sources, but in the early 1st century AD an Empire based out of Bactria emerged, called the Kushan Empire. The Kushans would expand to control a large territory, and it's in this period that the Bactrian language is first written down in its own right, using a modified version of the Greek alphabet with extra marks for sounds Greek didn't have. The Kushans oversaw an even more diverse religious and cultural environment than the Greeks had, tolerating the presence of Buddhism alongside the worship of Greek, Indic, Iranian, and Central Asian deities, along with the presence of Zoroastrianism.

Bactria became a stronghold of Buddhism, as well as a major trading presence along the early Silk Road, mainly facilitating trade between western China, Central Asia, and Northwestern India. The Sogdians to the north became a more important Silk Road presence but Bactrians remained a presence in the Gansu region, and probably in western China as well, and the Buddhist presence in Bactria continued to thrive. The region passed through several masters, but in the 7th century AD the Chinese envoy and explorer Xuanzang still reported a large and active Buddhist community in Bactria, and one that continued to produce new scholarly works.

Bactria, however, effectively came to an end with the Umayyad Caliphate's conquest of the Sassanid Empire. An important dynasty of Buddhists, the Bamarkids, converted to Islam, and the family became key advisors to Caliphs for some time afterwards, one member of this family being Jafar, and yes, he is the ultimate inspiration for that Jafar. The arrival of Islam gradually ended the prior religious environment; Buddhist institutions were particularly reliant on state support, and the conversion of key elites like the Barmakids started taking the legs out from under any specifically Bactrian religious traditions. In addition, Bactrian lost its official status, and it's believed the language became extinct some time in the 9th or early 10th century AD.

Thus we have our rough boundaries for Bactria and its existence.

(TO BE CONTINUED)