The strangers are, of course, the Chaldean invaders, and the prediction finds its fulfilment in the massacre of the princes of Judah at Ritdah (Jeremiah 52:9, Jeremiah 52:10), which was in Hamath, the northern border of Israel (1 Kings 8:65; 2 Kings 14:25).
Then they should see that their defiant speech as to the "caldron" and "the flesh" would be of no avail. Thus they should know that the prophet had spoken in the name of Jehovah, and that their punishment by the heathen was the righteous retribution for their having walked in the ways of the heathen.