This refers to the fifth year of Rehoboam's reign as king. Alternate translation: "in the fifth year that Rehoboam was king" or "in year five of King Rehoboam's reign" (See: [[rc://en/ta/man/translate/figs-explicit]] and [[rc://en/ta/man/translate/translate-ordinal]])
"Shishak, king of Egypt" here is a metonym for Shishak along with the Egyptian army. Alternate translation: "Shishak, king of Egypt, and his army with him, came up against Jerusalem" (See: [[rc://en/ta/man/translate/figs-metonymy]])