For, lo, I will raise and cause to come up against Babylon an assembly of great nations from the north country: and they shall set themselves in array against her; from thence she shall be taken: their arrows shall be as of a mighty expert man; none shall return in vain. An assembly of great nations - The army of Cyrus was composed of Medes, Persians, Armenians, Caducians, Sacae, etc. Though all these did not come from the north; yet they were arranged under the Medes, who did come from the north, in reference to Babylon.
Their arrows - They are such expert archers, that they shall never miss their mark.