Hezekiah rebelled against Assyria, and in 701 BCE Sennacherib came west to punish it. The Assyrian campaign took the fortified towns of Judah, and the siege of Lachish was carved in relief on the walls of Sennacherib's palace at Nineveh in such detail that archaeologists have matched the reliefs to the excavated siege ramp. Jerusalem itself was invested but not taken. The biblical account in Second Kings and Isaiah says the angel of the Lord struck the Assyrian camp and Sennacherib withdrew; the Assyrian annals, inscribed on clay prisms, describe shutting Hezekiah up in his royal city like a bird in a cage and taking heavy tribute, and conspicuously do not claim to have captured it.
Few reigns of this period can be read against an independent record at all, and fewer still against one written by the enemy. Two further classes of evidence attach to him directly. Jar handles stamped with a royal seal reading belonging to the king and a place name, the lmlk impressions, are concentrated in his reign and are usually read as provisioning for the war. And a clay sealing recovered from excavations beside the Temple Mount and published in 2015 reads, in the paleo-Hebrew script, as belonging to Hezekiah son of Ahaz king of Judah, an object from the king's own administration.
The tunnel is the third. A water channel more than five hundred metres long, cut through bedrock from the Gihon spring to the pool of Siloam, is described in Chronicles as Hezekiah's work, and an inscription found in it records two teams of quarrymen cutting toward each other and meeting in the middle. It was dug to secure the city's water against exactly the siege that came.