When Sauron succeeded in persuading Ar-Pharazôn to attack Valinor, the King set about building the greatest fleet that had ever been built. While the shipwrights were building and the arms being prepared, the Valar sent storms and omens out of the West, but the Númenóreans worked on.
At last, after nine years, the Armament was finished, and Ar-Pharazôn had a fleet that filled the seas west of Númenor. He boarded his flagship Alcarondas (the 'Castle of the Sea') and raised the signal to begin. Trumpets rang out throughout the fleet as it set sail into the West. There were so many ships that they surrounded Tol Eressëa completely, and they came at last to the shores of Valinor itself. But the Great Armament was for nothing: by the power of Eru the fleet was drawn back out to sea and down into the abyss, as was the island of Númenor where it had been built.