The poem recounts a story from the Bible, where Sennacherib, King of Assyria, lays siege to Jerusalem. Hezekiah, King of Jerusalem, prays, and in the morning 185,000 Assyrians are found dead in their camp
This is an unusual Romantic poem. This is an oddity of Byrons as he was a free thinker! Byron was a political radical thinker and the government of Britain was at the time quite tyrannical and oppressive, so the significance could be attack at this system.