The Syrians before, and the Philistines behind; or, the Syrians from the east, and the Philistines from the west. The Semitic races regarded the world as looking to the rising sun, and used for the east the preposition signifying "in front," for the west that signifying "behind."
Syria seems to have been hostile to Samaria until the league was formed between Rezin and Pekah, and may have become hostile again after Pekah's death (2 Chronicles 28:23). We read of a Philistine invasion of Judah in Chronicles (2 Chronicles 28:18), but not of their attacking Israel.
Still, it was as easy for them to attack the one as the other. They abutted on the territory of Israel towards the southwest, as Syria did towards the north-east. For all this his anger is not turned away; since Israel continued impenitent.
It would have ceased had they repented and turned to God (see Isaiah 9:13). His hand is stretched out; not to save, but to smite.