Compare this part of the daf to the stories in Shmuel Bet (Second Samuel) -- the son of Goliath is armed to go take vengeance on David. Ishbivenov is this same son of the giant, and his name is connected to his identity - because his revenge is on account of Nov. God makes it clear to David that he must pay the price of his wrong-doing, and gives him a choice of cutting off his descendants or suffer himself. He chooses the latter. Which leads to his own near-death, in greater detail in the Gemara than in the Navi. Also, the Assyrian army and their marching plan and huge numbers of troops (maybe). Plus, the angel Gavriel supporting the battles (against siege and more during Sennacherib's wars).