Many Greeks enter Iran under Seleucus's son,…

Many Greeks enter Iran under Seleucus's son, Antiochus I, and Hellenistic motifs in art, architecture, and urban planning become prevalent.

The Seleucids face challenges from the Ptolemaic kings of Egypt and from the growing power of Rome, but the main threat comes from the province of Parthia.

Arsaces (of the seminomadic Parni tribe), revolts against the Seleucid governor in 247 BCE and establishes a dynasty, the Arsacids, or Parthians, who will rule for nearly five centuries.