The Philistines were rejoicing because some king or nation that had oppressed them had lost its power. This may be a reference to David, since with the death of Ahaz, the power of the Davidic dynasty was at its lowest level so far. [1] It seems more likely, however, that Assyria is in view (cf. Isaiah 14:31-32). [2] The "rod" and the "serpent" could refer to ShalmaneserV, who laid siege to Samaria and dominated Israel for so long; and the "viper" and "flying serpent" could be SargonII, who followed Shalmaneser. This setback led the Philistines to think that this enemy would not oppress them any longer. But Isaiah warned that the oppressor was not gone forever. A worse enemy would come from that nation in the future, probably Assyria or Babylon ( Isaiah 14:29). Only the poorest of the people would survive the coming enemy. Most of the Philistines would starve or be slaughtered ( Isaiah 14:30). [source][source][source]
A disciplined enemy from the north would come against Philistia, totally demoralizing its inhabitants ( Isaiah 14:31). Evidently messengers from Philistia (and Egypt?) were seeking an alliance with Judea for mutual protection. The Lord advised the people, through Isaiah , to trust in Him, Zion being the place of His presence on earth, rather than in Philistia, since it was doomed ( Isaiah 14:32). [source][source][source]
Sargon II the Assyrian invaded Philistia in712 B.C, and in701 B.C. another Assyrian, Sennacherib, punished anti-Assyrian elements in Philistia. [source][source][source]