John Gill Commentary 2 Chronicles 32:2

"And when Hezekiah saw that Sennacherib was come, and that he was purposed to fight against Jerusalem," — 2 Chronicles 32:2 (ASV)

And when Hezekiah saw that Sennacherib was come Into the land of Judah, which he perceived and understood by reports brought to him: and that he was purposed to fight against Jerusalem; to besiege it and take it, if possible; this he saw was his design, by taking the fenced cities in his way, and coming forward with his forces.