Mighty Pharaoh, son of Ptolemaios who was the most trusted friend and general of Megas Alexandros. Your father seized for himself the mightiest lands of his general's empire, and wrought it into a mighty empire of his own - bequeathing it to you. By the might of his sword and his keen mind, your word is law along the length of the Nile, and the Western lands of the Pheoniceans and Judeans, and among the Northern islanders. Your rule is over the most prosperous land of Africa, and is the new home of a great rising of Greek thought, centered around Alexandria. But it is also a time of war; with the treacherous Seleukids, and the reckless Diadochoi of Megas Alexandros.
Your command is over one of the finest heavy phalangitai in the world, manned by a loyal corps of Greeks and Macedonians, attracted by your benevolent law. These men are supplimented by levies of the resettled Galatians and the conquored Judeans, forming their own light phalanx and auxiliaries. Though all of your land respect and admire your rule, those of the Nile are still as of yet wary of the approaching Hellenic armies and are still unreliable as anything but skirmishers. You can also hire Ethiopians from the lands south of Nubia as shock infantry, assured of their loyalty, as they share no ties with the Nubians and native Egyptians. But do not ignore the sea; Egyptians, Phoenicians and Kypriotai have since the time of Odysseus navigated the waters with ease. To control the waves of the eastern Mediterranean, is to control the whole coast.
Our position is strong and enviable. The mighty Neilos is our source of income, and must be protected accordingly. We have neighbours on all sides, but none of them trustworthy. To the South are the unruly Nubians, laden with the treasure of their gold mines; and the Karthadasti to the West, rich from their stock in the world's trade. To the North are the Antigonid Makedonians, who threaten to sweep across the independent Hellenes, to fragment your power among them. Finally to the East, is the great Seleukid behemoth, ever ready to amass and traverse the Sinai to our heartland.
The Seleukids claim that they are the true heirs to Alexandros, but their falsehoods are clear, as are those of their rivals. The flood of the Nile shall send our armies forth, to crush the false heirs of Zeus-Ammon's son
The Ptolemaic Empire, centered around the former Egyptian possessions of Alexander the Great, was founded by Ptolemy I Soter. Ptolemy was the son of Lagus, a Greek aristocrat in West Macedonia, but a few other reports might lead one to believe that he was an older illegitimate brother of Alexander himself. He was even raised to an extent alongside Alexander, and may have shared in his education under the tutelage of the great philosopher Aristotle.
Ptolemy accompanied Alexander throughout the entirety of his campaigns, serving as his general, becoming the satrap of Egypt after his death. After securing himself in Egypt, Ptolemy immediately shirked the authority of Alexander's temporary successor by killing the financial manager Alexander himself had appointed to manage Egypt, and subjugating the previously recognized independent city state of Cyrene. The singular act that led to his poor relations with his neighboring Diadochi though, was his seizure of Alexander's body; which he would later inter in Memphis.
This final act of defiance led the regent of Alexander's empire, Perdiccas, to lad an invasion of Egypt. Ptolemy however managed to repel his forces before they could cross the Nile. In response to his defeat, Perdiccas' deputies murdered him and retreated from his Ptolemy's Egyptian territories.
In 318, Ptolemy orchestrated his first occupation of Coele-Syria, which he held very briefly before withdrawing in the face of Antigonus' conquests in Asia - but his occupation of Cyprus at the same time was highly successful, despite a minor revolt orchestrated by Antigonus' agents.
In 312, Ptolemy and his temporary charge Seleucus, defeated Antigonus' son and deputy Demetrius at the Battle of Gaza. Afterwards, their forces once again occupied Coele-Syria, but again withdrew when Antigonus arrived with his own forces. To avoid further potential losses to Antigonus, Ptolemy agreed to a relatively equitable peace, and simply reoriented his attentions to some of Antigonus' more accessable possessions in Southern Asia Minor - which he seized easily. After securing the southern coast of Asia Minor, he moved on to Greece were he sized a number of cities, including Corinth.
With these new foreign territories secure, Antigonus chose to reconquor Cyprus, and defeated Ptolemy's brother in a decisive battle. When Antigonus tried to compound his victories by invading Egypt, Ptolemy repelled him easily, and responded with a new invasion of Coele-Syria. Based on false reports of more Antigonid victories, he withdrew, but reoccupied it when the error was exposed.
After Antigonus' defeat at Ipsus, Ptolemy withdrew from the conflicts over Greece and Asia Minor, and finally firmly subjugated Cyrene. A decade or so later in 285, Ptolemy abdicated his throne and dedicated himself to literature - even writing an account of Alexander's account, which would survive to form the basis of Arrian's chronicle.
Ptolemy's son, Ptolemy II, began his rule over a well organized and powerful kingdom - commanding a powerful force of Macedonian and Greeks that had been previously attracted by his father's liberal payment. Though he would eventually lose some of his possessions in Coele-Syria and Judea, his rule extended over most of Southern Asia Minor and even parts of Macedonia, thanks to successful naval engagements with the two dominant Greek powers of the time: the Macedons and the Seleucids. Having asserted his dominance, he agreed to a peace with the Seleucids, by which their new king married his daughter Berrenice around 250. During Ptolemy II's rule, his court at Alexandria was expanded physically and figuratively, with the addition of several new and lasting structures as well as the presence of numerous prominent period figures, prompting contemporary comparisons to King Louis XIV court at Versailles. He is also noted for the deification of his parents, and the marriage of his sister - a decision that embraced the Egyptian custom of familial marriage, so offensive to Greek morality.
Upon Ptolemy II's death, Ptolemy III came to power, and led a successful invasion of Syria in response to the murder of his sister Berenice in the Seleucid court. This invasion and subsequent occupation of some previously Seleucid territories, led to a renewal of hostilities between the two successor states. After his death, the Ptolemaic Empire entered it's first decline.
At this period of the greatest Ptolemaic ascendancy, a vapid and frivolous Ptolemy ascended the throne: Ptolemy IV. Ptolemy IV had many vices, and indulged in them frequently, to the chagrine of his foreign governors and advisors. Shortly after a massive bout of defections in his border provinces, this Ptolemy personally confronted the Seleucid king at Raphia, where he was victorious - preserving his kingdom as it was, for what was left of his rule.
After the death of his orgiastic father, Ptolemy V rose to the throne at the age of five. Before his rule could really begin, his empire had been irreperably damaged by a series of regents. During these regencies, he lost his possessions in Thrace and Macedon to the Macedonian King Philip, and Judea to the Seleucid King Antiochus III. During the actual years of his rule, the Egyptian natives - previously amicable to Ptolemaic rule for much of it's existence, began to rebel; depriving the Ptolemies of many border towns.
With the ascension of Ptolemy VI and his mother Cleopatra I to the throne, Egypt was set down the path of semi-vassalage to Rome. After his mother's death in 176, Antiochus IV invaded Egypt twice, each time successfully - but was forced to finally withdraw at the orders of a Roman envoy in the Ptolemaic capital. Late in his rule, Egypt came under the rule of a triumverate of a group of his relatives, until his death in combat against one of the later Seleucid kings in Syria.
The rule of Ptolemy VIII ended all semblance of Ptolemaic independence from Rome, which finally died when one of his co-rulers presented himself to the Roman senate asking for permission to invade Cyprus, which he succeeded at - though he was killed later attempted to recapture the rebellious Cyrene. With him dead, Ptolemy VIII secured his singular rule, and began a policy of mass state pogroms in Alexandria itself, killing local Jews and Greeks alike who opposed him.
In response to his behavior, the city revolted, forcing him to flee to Cyprus. His former wife, however, stayed in Alexandria to oppose the forces outside of the city - still loyal to Ptolemy. Though she held out for several years, the situation eventually became untenable, and she asked the Seleucids to aid her. Despite her request, the Seleucid's were unable to reach her, and she eventually was forced to flee to Syria - leaving Alexandria to be resecured by Ptolemy's forces.
Having restored himself to power, Ptolemy proceeded to engage in a disturbing series of internal family disputes, which lasted until his death in 116. At this point Cleopatra II returned to Egypt, but it had been left to Ptolemy's wife Cleopatra III. She attempted to install her son Alexander on the throne along with her, but the Alexandrians force her to select a less amicable candidate, though she quickly deposed him with false accussations of attempted murder. Despite this, her son Alexander had her assassinated in 101.
After Cleopatra's assassination, Ptolemy IX and Ptolemy X fought for almost three decades over the throne. Despite his seeming success in these political squabbles, Ptolemy X's eventual death allowed Ptolemy IX to hold the throne alone, and rule relatively smoothly until his death.
Berenice, Ptolemy IX's daughter took his throne after his death, but was forced to marry her stepson - who assassinated her shortly after in order to take the throne for himself. Despite his seemingly successful scheme, his murdered stemother/wife's supporters in Alexandria lynched him almost immediately after his actions, ending his several day rule in Egypt.
His stepbrother, Ptolemy XII ruled for 22 years as a co-regent with his wife and daughter, after his predecessors death. His rule was ended when he failed to respond to the Roman conquest of Cyprus, a region ruled by his own brother, forcing him to flee to Rome. After three years of his daughter's rule, he was reinstated in 55 by the Romans.
When Ptolemy XII became ill, his son Ptolemy XIII and his daughter Cleopatra VII jointly occupied the throne. When the brother tried to seize power with his elder regent, his sister fled to form her own army, initiating a new civil war within Egypt. Around this time, the Roman general Pompey fled his rival Julius Caesar, and sought refuge in Egypt - where he was beheaded, and presented to the visiting Caesar as a gift. While there, Caesar became Cleopatra VII's lover, and orchestrated her return to the throne. Despite Caesar's aid, her rivals tried to seize the throne, but a combined Roman-Egyptian army defeated and repelled their rebel army. 
As one of the Diadochi, the Ptolemaioi armies fight in the Macedonian tradition, with pike phalanxes as line infantry to tie down the enemy formations and cavalry to flank them. The Ptolemaioi also have other non-Hellenic troops to augment their Hellenic units, like Galatian & Ethiopian heavy infantry.