en_tn/2ki/19/14.md

this letter

This refers to the letter that King Sennacherib of Assyria sent to Hezekiah. (See: 2 Kings 19:8)

you are God alone

Hezekiah has changed from seeing Yahweh being Isaiah's God to Yahweh being the one and only God. The form of "you" in this location is emphatic. AT: "You yourself are God alone..."