The date is 721 BCE. All the nations around Judah have fallen to the Assyrian Empire except Jerusalem. The enemy is at the gates of the city. Sennacherib, king of Assyria sends the following message to Hezekiah, King of Judah.
"Do not listen to Hezekiah. This is what the king of Assyria says: Make peace with me and come out to me. Then every one of you will eat from his own vine and fig tree and drink water from his own cistern, until I come and take you to a land like your own, a land of grain and new wine, a land of bread and vineyards, a land of olive trees and honey. Choose life and not death! Do not listen to Hezekiah, for he is misleading you when he says, 'The LORD will deliver us.'" -- 2 Kings 18:31-32 (NIV)
The nation Judah had been paying tribute to Empire of Assyria since 742 BCE when King Ahaz pledged servitude to Assyria. Ahaz dies and his son, Hezekiah became king in 730 BCE. Hezekiah was a very good king and began restoring worship of God in the Temple. He removed all idols and stopped sending tribute to Assyria. He also had dug a water tunnel (1750 feet long) to save the city. In addition, he also had all the wells and water sources stopped up around the city of Jerusalem. Thus the attacking army could not find water to drink. Water still flows through "Hezekiah's Tunnel" today. Now it is 721 BCE and the message to the people of Judah is "Greater is He who is with us than he who is with them."
Isaiah encouraged King Hezekiah to withstand the offer of peace by Sennacherib, king of Assyria. Isaiah further prophesied that a large portion of Assyrian army would die in one night and the rest of the army and king would forthwith return to Assyria where the king soon died at the hand of his sons.
God Yahweh (YHWH) saved Judah during Hezekiah's life. God had added 15 years to Hezekiah's life due to his faithfulness (see II Kings 20:6). Manasseh, Hezekiah's son became the king when he died. He was an evil king and lost the Kingdom to Babylon in 606 BCE.