Joel 3:12
Let the heathen be wakened, and come up to the valley of Jehoshaphat: for there will I sit to judge all the heathen round about. Let the heathen be wakened, and come up to the valley of Jehoshaphat: for there will I sit to judge all the heathen round about.
The nations are wakened and brought up to stand before God, where He sits to judge all the heathen round about. That gathering brings His wrathful judgment upon the persecutors who enforced the mark of the beast. In that judgment His voice shakes the heavens and the earth. When shaken by that voice, those persecutors recognize their fatal error in turning away from what He spoke.