Shishak was the king of Egypt during the times of Solomon and Rehoboam. During Solomon's reign, an alliance was maintained through marriage, but during Rehoboam's reign, he broke away from the alliance and opposed Judah.
2 Chronicles 12:1In the fifth year of king Rehoboam, Shishak king of Egypt came up against Jerusalem, because they had trespassed against Yahweh,2 Chronicles 12:2with twelve hundred chariots, and sixty thousand horsemen. The people were without number who came with him out of Egypt: the Lubim, the Sukkiim, and the Ethiopians.2 Chronicles 12:3He took the fortified cities which belonged to Judah, and came to Jerusalem.2 Chronicles 12:4Now Shemaiah the prophet came to Rehoboam, and to the princes of Judah, who were gathered together to Jerusalem because of Shishak), and said to them, “Yahweh says, ‘You have forsaken me, therefore I have also left you in the hand of Shishak.’ ”2 Chronicles 12:5Then the princes of Israel and the king humbled themselves; and they said, “Yahweh is righteous.”2 Chronicles 12:6When Yahweh saw that they humbled themselves, Yahweh’s word came to Shemaiah, saying, “They have humbled themselves. I will not destroy them; but I will grant them some deliverance, and my wrath won’t be poured out on Jerusalem by the hand of Shishak.2 Chronicles 12:7Nevertheless they will be his servants, that they may know my service, and the service of the kingdoms of the countries.”2 Chronicles 12:8So Shishak king of Egypt came up against Jerusalem and took away the treasures of Yahweh’s house and the treasures of the king’s house. He took it all away. He also took away the shields of gold which Solomon had made.2 Chronicles 12:9King Rehoboam made shields of bronze in their place, and committed them to the hands of the captains of the guard, who kept the door of the king’s house.