Isa. 14:28-31; Book of Mormon Commentary, Reynolds & Sjodahl, 1:369
“The country of Philistia consisted essentially of five city-states, each governed by its own lord. The nation was home of the Philistines, detested enemies of Judah and the Israelites. This country was at the height of its power at the time of King Saul’s death, but declined during the reign of King David. The Philistines were conquered by the Assyrians in 734 B.C., later they became part of the Persian Empire, and finally the land was annexed to Syria by the Romans.” (Hoyt W. Brewster, Jr., Isaiah Plain and Simple, p. 148)
“A number of thorny, unresolved historical problems prevent the giving of a reasonably exact interpretation of some parts of the prophecy. But Isaiah seems to be telling Philistia not to rejoice over his predictions of the ruin and downfall of Judah, her traditional enemy. For whereas the kingdom of Judah will fall, there will come a glorious day when the people of Israel will rise above their troubles… . On the other hand, Philistia is to be ruined and to fall without having any prospects of recovery.” (Sidney Sperry, Book of Mormon Compendium, pp. 244-245)