Jamieson, Fausset and Brown on Isaiah 13:9

9. cruel--not strictly, but unsparingly just; opposed to mercy. Also answering to the cruelty (in the strict sense) of Babylon towards others (Is 14:17) now about to be visited on itself.

the land--"the earth" [Horsley]. The language of Is 13:9-13 can only primarily and partially apply to Babylon; fully and exhaustively, the judgments to come, hereafter, on the whole earth. Compare Is 13:10 with Mt 24:29; Re 8:12. The sins of Babylon, arrogancy (Is 13:11; Is 14:11; 47:7, 8), cruelty, false worship (Jr 50:38), persecution of the people of God (Is 47:6), are peculiarly characteristic of the Antichristian world of the latter days (Da 11:32-37; Re 17:3, 6; 18:6, 7, 9-14, 24).