...till he was strong

From 2 Chronicles 26:

And he did what was right in the eyes of the Lord, according to all that his father Amaziah had done. He set himself to seek God in the days of Zechariah, who instructed him in the fear of God, and as long as he sought the Lord, God made him prosper.

and...

In Jerusalem he made engines, invented by skillful men, to be on the towers and the corners, to shoot arrows and great stones.

but wait...

And his fame spread far, for he was marvelously helped, till he was strong.  But when he was strong, he grew proud, to his destruction.

you've got to read the whole chapter.