Some 2,700 years ago, King Sennachreib of Assyria begins his conquest of the Kingdom of Judah. King Hezekiah, direct descendant of King David, begins his preparations for the defense of the capital city of Judah, Jerusalem, including building a massive wall around the expanses of the city.
"When Hezekiah saw that Sennacherib had come, intent on making war against Jerusalem, he consulted with his officers and warriors about stopping the flow of the springs outside the city, and they supported him.
A large force was assembled to stop up all the springs and the wadi that flowed through the land, for otherwise, they thought, the king of Assyria would come and find water in abundance. He fortified the Millo of the City of David, and made a great quantity of arms and shields."
--- II Chronicles 32: 2 - 5