This is why he rebelled. Solomon had built the outer defense system (the Millo) and had restored the fortifications that were in disrepair from the time of his father David.
Jeroboam stood out during the construction as strong and able. When Solomon observed what a good worker he was, he put the young man in charge of the entire workforce of the tribe of Joseph.
One day Jeroboam was walking down the road out of Jerusalem. Ahijah the prophet of Shiloh, wearing a brand-new cloak, met him. The two of them were alone on that remote stretch of road.
Ahijah took off the new cloak that he was wearing and ripped it into twelve pieces.
Then he said to Jeroboam, "Take ten of these pieces for yourself; this is by order of the God of Israel: See what I'm doing - I'm ripping the kingdom out of Solomon's hands and giving you ten of the tribes.
In honor of my servant David and out of respect for Jerusalem, the city I especially chose, he will get one tribe.
And here's the reason: He faithlessly abandoned me and went off worshiping Ashtoreth goddess of the Sidonians, Chemosh god of the Moabites, and Molech god of the Ammonites. He hasn't lived the way I have shown him, hasn't done what I have wanted, and hasn't followed directions or obeyed orders as his father David did.
"Still, I won't take the whole kingdom away from him. I'll stick with him through his lifetime because of my servant David whom I chose and who did follow my directions and obey my orders.
But after that I'll remove the kingdom from his son's control and give you ten tribes.
I'll leave one tribe to his son, to maintain a witness to my servant David in Jerusalem, the city I chose as a memorial to my Name.
"But I have taken you in hand. Rule to your heart's content! You are to be the king of Israel.