Excerpts from Books and Wikipedia
"The Seleucid Empire (...) was a Hellenistic state ruled by the Seleucid dynasty which existed from 312 BC to 63 BC; Seleucus I Nicator founded it following the division of the Macedonian Empire vastly expanded by Alexander the Great. Seleucus received Babylonia (321 BC) and from there expanded his dominions to include much of Alexander's near-eastern territories. At the height of its power, the Empire included central Anatolia, Persia, the Levant, Mesopotamia, and what is now Kuwait, Afghanistan, and parts of Pakistan and Turkmenistan.
. . . Seleucus I entered into an agreement with Chandragupta whereby he ceded vast territory west of the Indus, including the Hindu Kush, modern-day Afghanistan, and the Balochistan province of Pakistan and offered his daughter in marriage to the Maurya Emperor to formalize the alliance. . . . However, the Seleucid kings continued to rule a rump state from Syria until the invasion by Armenian king Tigranes the Great in 83 BC and their ultimate overthrow by the Roman general Pompey in 63 BC." [Wikipedia]