What does Isaiah 20:1 mean?

Chapter 20 finishes Isaiah's oracle from the Lord against Egypt (Isaiah 19:1). The prophet sets the events of this passage at a specific time in the world's history. This moment was when Sargon, king of Assyria, sent his commander to defeat the rebellious Philistine city of Ashdod. This figure is referred to using the Hebrew word tartān', which seems to be a title rather than a proper name (2 Kings 18:17).

Modern scholars locate this event in the year 711 BC. This data comes from two other sources that back up Isaiah's reference of this battle. One source is the Assyrian Annals of Sargon II; those detail the history of Assyria from the emperor's perspective. Sargon ruled Assyria from 722–705 BC. His annals report this campaign against Ashdod were between 712–711 BC. In addition, fragments of a similar inscribed pillar were found in Ashdod in 1963 that also hail Sargon's victory at this same time.

Apparently, the king of Ashdod had made some kind of alliance with Egypt for mutual support against Assyria. When Ashdod made this agreement, they stopped paying tribute to the Assyrians. When the Assyrians came to attack Ashdod, the Egyptians did not help. The Egyptians even turned over the king of Ashdod to the Assyrians when he tried to find asylum in Egypt after his defeat.

The Lord's continuing point to His people is that they should not put their hope and trust in other nations. Those nations cannot save them from the Assyrians. Ashdod looked to other nations for protection, and that turned out negatively for them. Instead, the Lord wants His people to trust Him, and Him alone, to protect them from their powerful enemies.