Answer
Hezekiah submitted to Sennacherib after the Levantine War of 701 BC. The war was fought between the Kingdom of Judah and the Neo-Assyrian Empire. The war started when Sennacherib invaded Judah and laid siege to Jerusalem. Hezekiah surrendered to Sennacherib in order to avoid the destruction of Jerusalem. As a result of the war, Judah became a vassal state of Assyria.