The Seleucid Empire was one of several political states founded after the death of Alexander the Great, whose generals squabbled over the division of Alexander's empire.
The partition of Alexander's empire (323-281 BC)
Alexander the Great left a huge empire of Persio-Greek culture to his successors (the Diadochi or Diadochoi), who jostled for supremacy over portions of his empire.
The Seleucid Empire, was founded in 323 BC by Seleucus I Nicator and had its capital at Babylon. It controlled a large region including modern-day Syria, Lebanon, Jordan, Mesopotamia, Persia, and Bactria (eastward to the Indus River).
Invasion and loss of India (304 BC)
Seleucus I invaded India (modern Punjab in northen India and Pakistan) in 304 B.C., which was then the Mauryan empire ruled by Chandragupta Maurya. It is said that Chandragupta put an army of 100,000 men and 9,000 war elephants and forced Seleucus to conclude an alliance and to give him his daughter in marriage.
Seleukos sent an ambassador named Megasthenes to Chandragupta's court, who repeatedly visited Pataliputra (modern Patna in Bihar state), capital of Chandragupta. Megasthenes has written detailed descriptions of India and Chandragupta's reign.
Death of Seleucus I (281 BC)
Other territories were lost (Gedrosia on the coast of the Arabian Sea and Arachosia on the west of the Indus River) until Seleukos was assassinated in 281 B.C. The Seleucid empire disintegrated soon after into Parthia (Arsaces as King), Syria (Antiochus I as king) and Bactria (Diodotus as king).
Greco-Bactrian secession (250 BC)
Diodotus, who was governor for the Bactrian territory asserted independence in 250 BC to form the Greco-Bactrian kingdom. This kingdom was characterized by a rich Hellenistic culture, and was to continue its domination of Bactria until around 125 B.C. when it was overrun by the invasion of northern nomads. One of the Greco-Bactrian kings Demetrius I of Bactria invaded India from 180 B.C. to form the Greco-Indian kingdom, which was to last until 1 B.C.
Parthian secession (250 BC)
In the West, Syria was governed by Antiochus I.
Greece campaigns (192 BC)
The Seleucids subsequently declined, and the Seleucid dynasty itself eventually vanished in the mid-1st century BC.
There were over 30 kings of the Seleucid dynasty from 323 to 60 BC.