Ashdod is Israel's fifth largest city and continues to be an important port city with many archaeological finds. 

During biblical times, Ashdod was populated by the Philistines who settled in an area southeast to the port and the Israelites couldn't conquer Ashdod from them.

Ashdod was known for having two cities during the Philitines time, Ashdod Yam, the seaside town, and Tel Ashdod, an inland town. These two cities coexisted and Ashdod Yam was a very important port of trade.

 

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One of five principal cities of the Philistines, where the Philistines defeated Israel and captured the ark of the covenant.
Ashdod was 10 miles north of Ashkelon and two and a half miles east of the Mediterranean Sea on the Philistine plain. It was the northernmost city of the Philistine Pentapolis recorded in Josh. 13:3. Ashdod occurs in written history first in the Late Bronze period where it is mentioned in the trade documents of the Ras Shamra tablets discovered at Ugarit (ancient trade center near the Mediterranean coast in northern Syria). Ashdod is described as a manufacturer and exporter of textiles, specifically purple wool. The city name also occurs in the Egyptian list of names , Onomasticon of Amanope (263).

“ASHDOD,” Holman Illustrated Bible Dictionary, paragraph 1627.

n the OT Ashdod was a place where some of the Anakim remained during the time of Joshua (Josh. 11:22). As one of the five chief cities of the Philistines, it stood yet to be possessed by Joshua (Josh. 13:3), who allocated it to the tribe of Judah (Josh. 15:46-47). David subdued the Philistines, implicitly including Ashdod (2 Sam. 5:25; 8:1), but it was not described as under Israel’s control until Uzziah (783–742 B.C.) captured it (2 Chron. 26:8). Perhaps the most infamous contact between Ashdod and Israel is reported in 1 Sam. 4–6 when the Philistines defeated the army of Israel in battle, killed the two sons of Eli, Hophni and Phinehas, and captured the ark of the covenant. See Anak, Anakim.

“ASHDOD,” Holman Illustrated Bible Dictionary, paragraph 1629.

Tel Ashdod, 6 km SE of the modern village, was a major Philistinian city, first mentioned in Late Bronze Age texts (Jos. 11:22) dealing with Ugarit. It may have withstood attempts by Judah to conquer it and settle there (Jos. 13:3; 15:46–47). It had a principal port (Ashdod-Yam; in Akkadian sources Asdudimmu cf. ANET, p. 286) and a temple of Dagon to which the ark was taken (1 Sa. 5:1ff.). It was attacked by Uzziah of Judah (2 Ch. 26:6). When it rebelled against Assyria, who replaced King Azuri by his brother, Asdudu was sacked, according to Assyr. inscriptions, by Sargon II in 711 BC. These calamities were noted by Amos (1:8) and Isaiah (20:1). Later besieged by Psamtik I of Egypt for 29 years (Herodotus 2. 157), it became a Bab. province and was weak (Je. 25:20) and derelict (Zp. 2:4; Zc. 9:6). It was partially repopulated after the Exile (Ne. 13:23–24). As Azotus, its idolatry provoked attacks by the Maccabeans (John the Hasmonean and John Hyrcanus, 1 Macc. 5:68; 10:84). Separated from Judaea by Pompey (Jos., BJ 1.156), reconstructed by Gabinius, and given to Salome, Herod’s sister, by Augustus, it flourished (Acts 8:40) until it surrendered to Titus.

“Ashdod,” NBD, 91.

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The Philistines were ruled by five rulers, not just one. Each ruler ruled from a different city—Ashdod, Ashkelon, Ekron, Gath, or Gaza. Each of these cities was an important center for trade and commerce. Given Delilah’s character, it is little wonder that she betrayed Samson when these rich and powerful men paid her a personal visit.

The conquest of northern Canaan was complete; this passage summarizes Joshua’s achievements. Verses 18–20 state the historical and theological justification for the conquest: the Canaanites (with the exception of the Gibeonites) had refused to make peace with Israel, for God had hardened their hearts so that he might destroy them without mercy. (On the justification for their extermination, see note on 6:17.) It is note-worthy that in 11:22 no mention is made of the Philistines, who had not yet migrated to Gaza, Gath and Ashdod. This is an incidental indicator of the age of the narrative, refuting contemporary critical theories that date the book much later.

Ted Cabal, ed., The Apologetics Study Bible, Nashville: Holman Bible Publishers, 2007, paragraph 2023.