Ether 7:5

And when he had gathered together an army, he came up unto the land of Moron where the king dwelt, and took him captive, which brought to pass the saying of the brother of Jared, That they would be brought into captivity.

Corihor gathered an army. He came to the land of Moron where the king lived. He took the king as his prisoner. This is what the brother of Jared had said would happen. He had said they would be taken as prisoners.

Once Corihor had raised an army, he marched to the land of Moron where the king lived and took him captive. This fulfilled what the brother of Jared had warned—that they would be taken captive.