When in 301, after the battle of Ipso, a kind of equilibrium was created in the Hellenistic world, he was able to regain possession of Cyrenaica and Cyprus and of Celesiria, which became the bone of contention almost incessant between his dynasty and that of Seleucids. In 287 the king of Egypt succeeded in affirming and extending his protectorate over the Cyclades. His two first successors added other conquests on the coasts of Asia Minor and even in Thrace and the Hellespont, but if this proves that they valued the dominance of the Eastern Mediterranean very much, we must not forget that Ptolemy II already pushed the borders of Egypt south, beyond the first cataract, towards Nubia, and that he founded many farms on the African coasts of the East, up to Cape Guardafui. In 285 the founder of the dynasty, concerned with ensuring its stability, associated the throne with his son born to him by Berenice (I) in 308, in Cos, during the expedition to the Cyclades. He died leaving to his successor the more united, more solid and better governed kingdom that had arisen from the ruins of the Alexander empire.
According to insidewatch.net, the successor of the first Lagide, who also had a very long reign of 38 years, is known by the epithet of Philadelphus, a title indeed due to his sister Arsinoe II (v.) Who had a very considerable part in the affairs of the kingdom and whom he later married having repudiated his first wife, but he could rightly be called the Magnificent for the impetus given to the building development of the new capital, to the arts, sciences, letters, geographical and commercial explorations, for the extraordinary passion he had to organize grandiose games and sumptuous ceremonies. On the other hand, the reclamation of the Arsinoite (oasis of el-Fayyūm) and the open roads through the eastern desert, or the resumed excavation of the canal built by Neco and reactivated by Dario, between the apex of the Delta and the current Gulf of Suez.alexandria; which is also referred to for art in the Alexandrian period). The most notable military events that took place during his reign were the war against his half-brother Magas, who proclaimed himself independent in Cyrene (274), and the subsequent war against the Seleucids. Both closed in his favor. Syria, Caria and Miletus were lost to Antiochus. After the death of his sister and wife Arsinoe II in 271-70, Ptolemy II did not pursue the policy of alliance with the Athenians and the other Hellenes with farsighted energy, and his inaction caused Athens to fall into the power of Antigonus. He then caused the Egyptian fleet to suffer a serious defeat near Cos, which, however, did not seriously shake the power of Egypt. With Cyrene the dispute was closed by establishing that the little princess Berenice would become the bride of the crown prince of Egypt. The Second Syriac War, provoked by Antiochus II, who succeeded his father in 261, also ended in marriage (252). The daughter of Ptolemy II, Berenice, married Antiochus, who divorced his first wife for this purpose. But the peace between the two dynasties was not lasting. In fact, Ptolemy III Evergete who succeeded his father in 247, reunited Cyrenaica with Egypt for the marriage with the daughter of Magas, Berenice II (v.), Almost immediately moved against Syria to avenge his sister who repudiated her first wife of Antiochus, Laodice, had expelled from the throne and had him assassinated. The result of the enterprise was excellent. He could easily have occupied all of the Seleucid Empire had it not been recalled to Egypt by a revolt of the indigenous element. The internal conditions of the Seleucid dynasty, given the fraternal struggle that lasted several years between Seleucus II and Antiochus Ierace, allowed Ptolemy III to reject the attempts of revenge (240) and to attend to the works of peace: construction and restoration of sanctuaries dedicated so much to Hellenic deities as for the natives, in Alexandria, in Canopus, along the Nile valley: in Edfu, in Thebes and elsewhere up to Aswan; provisions in favor of his veterans and agricultural works and even, preceding Julius Caesar by more than two centuries, the reform of the Egyptian calendar. The 25 years of reign of this sovereign, a brave but peace-loving warrior and respectful of treaties, mark the highest degree of power,
A much less brilliant period, indeed of true decline, begins with his son and successor Ptolemy IV Philopator (221). The power abroad begins to decline; the government is weakening internally and dynastic conflicts begin to divide the country into two adverse camps. This king, naturally more inclined to literary idleness, to feasts and to the pleasures of the senses than to the care of power, surrounded by depraved and crafty advisors, did not take long to stain himself with the killing of his brother Magas preferred by the energetic mother Berenice II of Cyrene, whom he also did or allowed to be assassinated.