Arsames I apparently takes control of Commagene, Sophene and Armenia in the year 260 BCE after the death of his grandfather Orontes III, king of Armenia, and his father Sames, king of Commagene.

Quite why they both die in the same year is not recorded, though it looks suspicious.

It is known the Seleucid Empire was always trying to overthrow the Armenian dynasties who still ruled the lands their forebears had in the time of the Achaemenid Empire.

Ziaelas of Bithynia finds refuge at the court of king Arsames, and upon the death of king Nicomedes I of Bithynia Ziaelas returns to take the kingdom in 254 BCE.

The Macedonians, especially Seleucus I and his son Antiochus I, have established the Seleucid Empire and founded great many Greek towns in the region of present Afghanistan, where the Greek language will become dominant for some time.

The paradox that Greek presence is more prominent in Bactria than in areas far closer to Greece can possibly be explained by past deportations of Greeks to Bactria.

For instance, during the reign of Darius I, the inhabitants of the Greek city of Barca, in Cyrenaica, were deported to Bactria for refusing to surrender assassins.

In addition, Xerxes also settled the "Branchidae" in Bactria; they were the descendants of Greek priests who had once lived near Didyma (western Asia Minor) and betrayed the temple to him.

Herodotus also records a Persian commander threatening to enslave daughters of the revolting Ionians and send them to Bactria.

However, these few examples are not indicative of massive deportations of Greeks to central Asia.

Considerable difficulties faced by the Seleucid kings and the attacks of Ptolemy II of Egypt give Diodotus, satrap of Bactria, the opportunity to declare independence (about 255 BCE) and conquer Sogdiana.

He is the founder of the Greco-Bactrian Kingdom.

The new kingdom, highly urbanized and considered as one of the richest of the Orient, is to further grow in power and engage into territorial expansion to the east and the west.

The newly declared King marries a daughter, born around 266 BCE, of Antiochus II Theos and wife Laodice I and has two children: Diodotus II and a daughter, born around 250 BCE.

The Seleucid kingdom, a major center of Hellenistic culture, maintains the preeminence of Greek customs and manners over the indigenous cultures of the Middle East.

A Greek-speaking Macedonian aristocratic class will dominate the Seleucid state throughout its history, although this dominance is most strongly felt in the urban areas.

Antiochus II, who succeeds his father in 261 BCE, has begun a new war for Syria.

He reaches an agreement with the current Antigonid king in Macedon, Antigonus II Gonatas, who is also interested in pushing Ptolemy II out of the Aegean.

With Macedon's support, Antiochus II launches an attack on Ptolemaic outposts in Asia.

Most of the information about the Second Syrian War has been lost.

It is clear that Antigonus' fleet defeated Ptolemy's at the Battle of Cos, diminishing Ptolemaic naval power.

Ptolemy appears to have lost ground in Cilicia, Pamphylia, and Ionia, while Antiochus regains Miletus and Ephesus.

Macedon's involvement in the war ceases when Antigonus becomes preoccupied by the rebellion of Corinth and Chalcis in 253 BCE, possibly instigated by Ptolemy, as well as an increase in enemy activity along Macedon's northern frontier.

The war is concluded around 253 BCE with the marriage of Antiochus to Ptolemy's daughter, Berenice Syra.

Antiochus repudiates his previous wife, Laodice, and turns over substantial domains to her.

A Jewish diaspora grows, as cities like Alexandria, the Ptolemid capital, begin to acquire a substantial Jewish population.

Hellenistic Jews at Alexandria produce the Septuagint, the first version of the Hebrew Bible in Greek, the lingua franca throughout the region. (The name Septuagint, from the Latin septuaginta, “seventy”, is a later derivation from the legend that there were seventy-two translators, six from each of the twelve tribes of Israel, who worked in separate cells, translating the whole, and ultimately all their versions were identical. There are in fact large differences in style and usage between the Septuagint's translation of the Torah and its translations of the later books in the Old Testament. A tradition that translators were sent to Alexandria by Eleazar, the chief priest at Jerusalem, at the request of Ptolemy II Philadelphus, a patron of literature, first appeared in the Letter of Aristeas, an unreliable source.)

Analysis of the language has established that the Torah, or Pentateuch, was translated near the middle of the third century BCE and that the rest of the Old Testament was translated in the second century BCE.

Ptolemy II extends Alexandria, which is rapidly becoming the literary and scientific center of the Hellenistic world, and wins renown as a great patron of the arts and sciences.

Zenon, the confidential business manager of Philadelphus' chief minister, is in 259 sent to Palestine and Syria, where his master has commercial interests.

His letters speak particularly of a trade in slaves, especially of young girls for prostitution, in whom there appears to have been a brisk trade, with export to Egypt.

Zenon's records also testify to a considerable trade in cereals, oil and wine.

Egypt's victories in the First Syrian War have solidified the kingdom's position as the undisputed naval power of the eastern Mediterranean; Ptolemy’s fleet (one hundred and twelve ships) bears the most powerful naval siege units of all time, guaranteeing the king access to the coastal cities of his empire.

The Ptolemaic sphere of power extends over the Cyclades to Samothrace, and the harbors and coast towns of Cilicia Trachea, Pamphylia, Lycia and Caria.

Antiochus II Theos, king of the Seleukid realms, launches the Second Syrian War against Ptolemy to avenge his father's losses in Phoenicia and Anatolia.

Gonatus, almost immediately after the war, joins forces with the Seleucid king Antiochus II Theos, who had succeeded his father, Antiochus I, in 260 BCE, against their common enemy Ptolemy II Philadelphus, ruler of Hellenistic Egypt.

The defeat of the Egyptian fleet at sea by Antigonus II Gonatus of Macedon enables Antiochos to regain control of the Mediterranean ports lost by his father in the First Syrian War.

Antiochus reconquers much of Anatolia, including the cities of Ephesus and …

…Miletus.

Antiochus having overthrown a tyrant of Miletus after he recaptured the city, the citizens worship him in thanksgiving as a god.

He later organizes an empire-wide cult, as suggested by his epithet, Theos (God).

He also establishes the freedom of the other Ionian cities.

Further, he continues his predecessors' policies of encouraging the foundation of cities in his realm.