For many years there was no reference to Sargon II (722-705 B.C.) in the available Assyrian records. Yet, the prophet Isaiah, writing at the time of the Assyrian captivity of the northern kingdom of Israel, mentions Sargon’s campaign against Ashdod.
In the year that the commander in chief, who was sent by Sargon the king of Assyria, came to Ashdod and fought against it and captured it– (Isaiah 20:1 ESV)
The palace of Sargon was discovered by Emile Botta at Khorsabad in 1843. This was the period of “monumental” discoveries in archaeology. Both the British Museum and the Louvre have impressive artifacts from the palace of Sargon. The photo below shows Sargon (on the left) receiving one of his ministers.
D. J. Wiseman explains the historical context of what happened at Ashdod.
In 716 bc Sargon sent his army commander (turtan; the *‘tartan’) to war against the Arabs in Sinai. This led to the reception of tribute from the pharaoh Shilkanni (Osorkon IV) of Egypt and from Samsi, queen of the Arabs. Despite these Assyrian successes, the people of Ashdod displaced their Assyrian-nominated ruler, Ahimetu, by a usurper Iadna (or Iamani) who initiated yet another Syro-Palestinian league against Assyria, doubtless relying on Egyptian help. In 712 bc the same turtan was sent to conquer Ashdod (Is. 20:1), which was reduced to the status of an Assyrian province. Since Azaqa (’Azeqah or Tell es-Zakariye) on the Judaean border near Lachish surrendered in this campaign, it will be seen how narrowly independent Judah escaped a further invasion. Iamani fled to Nubia for refuge, only to be extradited to Nineveh by the ruler Shabaka. (The New Bible Dictionary, 3rd edition)
One hundred twenty years after the discovery of Sargon’s palace, archaeologists working at Ashdod discovered fragments of a cuneiform stele of Sargon II at Ashdod. For more information about the discovery and a photograph of it see “Sargon II, Ashdod, and Isaiah 20:1” here.