Next to Jerusalem Lachish is the key city of Judah. It was captured by Sennacherib and by Nebuchadnezzar on their approach to attack Jerusalem.

This is an image of the tel of Lachish.

The structure on the right side of the tel is the siege ramp built by Sennacherib and the Assyrians in 701 BC.

The Assyrian Siege ramp built to take the city. This ramp can be seen in Assyrian reliefs in the palace in Nineveh. Sennacherib devoted an entire room to this battle and guarded it with a series of three pairs of colossal human-headed winged bulls.

Watch Slide Show of the Assyrian carvings that tell this story
HERE

A close up of the Sennacherib's siege ramp.

I think he was trying to get as much credit and security from this victory since he was annihilated later when he was approaching Jerusalem.