Albert Barnes Commentary Joshua 10:3

"Wherefore Adoni-zedek king of Jerusalem sent unto Hoham king of Hebron, and unto Piram king of Jarmuth, and unto Japhia king of Lachish, and unto Debir king of Eglon, saying," — Joshua 10:3 (ASV)

For Hebron, see (Genesis 13:18). Jarmuth, later one of the cities of Judah (Joshua 15:35), is probably identified with the modern Yarmuk. Lachish was also a city of Judah (Joshua 15:39) and, like Jarmuth, was occupied by Jews after the captivity (Nehemiah 11:39). It was fortified by Rehoboam after the revolt of the ten tribes (2 Chronicles 11:9) and seems to have been regarded as one of the safest places of refuge (2 Kings 14:19). Through Lachish, the idolatry of Israel was imported into Judah (Micah 1:13), and the capture of the city by Sennacherib was the punishment for this sin (2 Kings 18:14–17; 2 Kings 19:8). Lachish is by most authorities identified with Um Lakis, lying some twenty miles west of Eleutheropolis, on the road to Gaza (and by Conder with El Hesy).

Eglon is the modern Ajlan.