Although Isaiah does not identify the peoples spoken of here, it is thought that Isaiah 17:12–14 describes the arrival of the Assyrian army.
The Assyrian army consisted of people from many different nations. Furthermore, in Isaiah 8:6–8, images of waves and raging water are also used to describe the nation of Assyria.
12 Ah, the thunder of many peoples; they thunder like the thundering of the sea! Ah, the roar of nations; they roar like the roaring of mighty waters!