Philistia
These people were also known as the Sea Peoples. They came from Caphtor (Jeremiah 47:4). There is confusion on where Caphtor is, and I will investigate this matter (Cappadocia, MacArthur, 1124; Crete or Cyprus, Howe, 86). They had failed to take out the Egyptians, but they gained control of the border in the northeast by 1125 B.C. This came to be known as Philistia. There were five city-states there: Ashkelon, Ashdod, Ekron, Gath, and Gaza. They had superior iron weapons and a well-disciplined military that kept the Hebrews away from their settlements (Howe, 86).
Sources
Howe, Helen and Robert Howe. Ancient and Medieval Worlds. White Plains: Longman, 1992. Chapter 4.
MacArthur, John. The MacArthur Study Bible. Nashville, Word: 1997.