Osorkon IV ascended to the throne of Tanis in c. 730 BC,[4] at the end of the long reign of his predecessor Shoshenq V of the 22nd Dynasty,[5][6][7][8] who was possibly also his father.

[9] However, this somewhat traditional collocation was first challenged in 1970 by Karl-Heinz Priese, who preferred to place Osorkon IV in a lower–Egyptian branch of the 23rd Dynasty, right after the reign of the shadowy pharaoh Pedubast II;[10] this placement found the support of a certain number of scholars.

Along with other rulers of Lower and Middle Egypt – mainly Nimlot of Hermopolis and Iuput II of Leontopolis – Osorkon IV joined the coalition led by the Chief of the West Tefnakht in order to oppose the Nubian.

As reported on his Victory Stela, Piye accepted their submission, but Osorkon and most of the rulers were not allowed to enter the royal enclosure because they were not circumcised and had eaten fish, both abominations in the eyes of the Nubian.

For reasons which remained unknown – possibly in order to remain neutral towards the powerful Neo-Assyrian Empire, or simply because he did not have enough power or resources – King So did not help Hoshea, who was subsequently defeated and deposed by Shalmaneser V. The Kingdom of Israel ceased to exist, many Israelites were brought to Assyria as exiles,[24] and Assyrian and Babylonian settlers occupied Israel.

Some archaeological findings[31] suggest that shortly after this date, Bocchoris (Bakenrenef) of the 24th Dynasty may have expanded his realm eastward, supplanting Osorkon at Tanis.

[35] A few years later a man called Gemenefkhonsbak, possibly a descendant of the now-defunct 22nd Dynasty, claimed for himself the pharaonic royal titles and ruled in Tanis as its prince.

[47] Shilkanni is reported by Assyrians as "King of Musri": this location, once believed to be a country in northern Arabia by the Orientalist Hans Alexander Winckler, is certainly to be identified with Egypt instead.

[66] Furthermore, in 2010/11 a French expedition discovered in the Temple of Mut at Tanis two blocks bearing a relief of a King Usermaa(t)re Osorkonu, depicted in a quite archaizing style, which at first were attributed to Osorkon III.