This is the day that is coming to destroy all the Philistines.
The reference to the day that is coming
makes it clear that it is the time that the Lord has determined (see Jeremiah 46:10, Jeremiah 46:21).1
All the Philistine includes Tyre and Sidon. These are two Phoenician cities to the north that were probably in some kind of treaty with the Philistines. These events are happening because, The Lord is destroying the Philistines, the remanent of the coastlands of Caphtor.
Caphtor refers to Crete, which is where the Philistines originally came from (see Amos 9:7).2
4 Parce que le jour arrive où seront détruits tous les Philistins, Exterminés tous ceux qui servaient encore d'auxiliaires à Tyr et à Sidon; Car l'Eternel va détruire les Philistins, Les restes de l'île de Caphtor.