Around 300 BC
, some new people invaded West Asia
in the north. These people were called the Parthians
. Like the Scythians, and like the Persians when they first came to West Asia
, the Parthians were nomadic
people. They travelled around Siberia with their horses and their cattle, and grazed the cattle and the horses on the great fields of grass there. Usually they lived well enough this way.
But sometimes the weather was worse than usual, and the Parthian cattle could not find enough to eat. This time, when that happened, the Parthians headed south into Alexander's
empire. Maybe they had heard that Alexander had died and they thought it would be easy to take over. Maybe they just thought it would be nicer in the south, where it was warmer.
The Parthians immediately succeeded in taking over the middle part of Alexander's empire (roughly modern Iran). This split the Greek
empire in half, leaving the Greek colonies in Bactria (modern Afghanistan) isolated. They stayed there for about 200 years, gradually learning the culture of West Asia. They converted to Zoroastrianism