Jamieson, Fausset and Brown on Isaiah 47:6

6. reason for God's vengeance on Babylon: in executing God's will against His people, she had done so with wanton cruelty (Is 10:5, &c.; Jr 50:17; 51:33; Zec 1:15).

polluted my inheritance--(Is 43:28).

the ancient--Even old age was disregarded by the Chaldeans, who treated all alike with cruelty (La 4:16; 5:12) [Rosenmuller]. Or, "the ancient" means Israel, worn out with calamities in the latter period of its history (Is 46:4), as its earlier stage of history is called its "youth" (Is 54:6; Eze 16:60).