On the death of Nimlot (the previous High Priest of Thebes), Takelot II decided against letting the sons of Nimlot (or Harsiese B, the possible grandson of Harsiese High Priest and King of Thebes), to inherit the High Priest post. Instead Takelot II decided to appoint his son - the Crown Prince Osorkon. It was a decision that would provide costly for Egypt. Harsiese B did not take kindly to being overlooked, even the role of 2nd Prophet was denied him (this went to Prince Djedptahefankh D), Harsiese B now became the main focus of Theban discontent for Tanis.
In Year 11 Prince Osorkon sailed for Thebes, encouraged by the god Arsaphes to 'suppress wrong-doing'. The journey south was spent on works of restoration and supressing any opponents that stood against him. On reaching Thebes, priests accused of 'irregularities' in the administration and cult of the temple were tried, executed and had their corpses burnt. Following this show of force Prince Osorkon would return three times a year for the great festivals and also the keep the king's stamp of authority on Thebes.
In Year 15 suddenly and unexpectedly Egypt was enveloped in civil war, this was due to last for nearly 10 years - until Year 24 of Takelot II. A policy of reconciliation was adopted it agreed that the repressive tactics of Prince Osorkon had failed. A fleet of the king's ships sailed for Thebes again led by Prince Osorkon - once there he made rich offerings to Amun, and promised gifts in years to come, thus insuring peace in Egypt.
The death of Takelot II
Peace lasted in Egypt for 2 years, until once again in Year 26 Thebes and the land south suddenly erupted into civil war. This last act of defiance from Thebes seems to have been the final undoing for Prince Osorkon, an inscription of the time states '.... he was there quite alone, such that there was not one friend [with him(?)]. Thebes had won its independence from Tanis, Osorkon had lost his position of the High Priest and most probably lost control of Upper Egypt too.
But this was to carry an even worse disaster for Prince Osorkon: while the prince was still absent from Tanis, the King Takelot II died and a younger brother Shoshenq became the next pharaoh - Shoshenq III. Although Prince Osorkon was the Crown Prince and heir to the throne he had lost his right to kingship and was to serve under this new king. Shoshenq III also accepted Theban demands to decide their own High Priest and finally Harsiese B was given the office, in return Thebes accepted Sheshonq III (for a while) as their rightful king.