Isaiah 30:13-14

Consequently their iniquity would lead to disaster, similar to the sudden internal collapse of a high wall, and the severe external smashing of an earthenware jar. It would be complete, as when no useful pieces remain after the smashing of a pot. That judgment had not yet come was hardly grounds for concluding that it would not come (cf. Matthew 24:36-44; Mark 13:32-37; 2 Peter 3:3-10).

"The interval from the first cracks until the actual collapse [of a wall] may be a long time, but when the collapse comes it is terribly sudden and irreversible. So it will be with this refusal to rely on God. Years may pass, but one day the Assyrians will stand at the door with all Judah in ruins behind them." [Note: Oswalt, p. 554.]

When God miraculously slew Sennacherib’s besieging forces around Jerusalem in 701 B.C., the Assyrians had already destroyed much of Judah.