What does 2 Kings 19:9 mean?

When the king of Assyria heard that King Tirhakah of Cush was coming to fight him, he sent messengers again to Hezekiah, saying, 2 Kings 19:9 - Modern Text Bible

(The Assyrian king, Sennacherib, learns that another powerful army is approaching, so he tries to pressure Hezekiah again before things get worse for him.)