The city was unbelievably devastated. Of its 90,000 buildings, over 60,000 were demolished. Another bomb was assembled at Tinian Island on August 6. On August 8, Field Order No.17 issued from the 20th Air Force Headquarters on Guam called for its use the following day on either Kokura, the primary target, or Nagasaki, the secondary target. Three days after Hiroshima, the B-29 bomber, "Bockscar" piloted by Sweeney, reached the sky over Kokura on the morning of August 9 but abandoned the primary target because of smoke cover and changed course for Nagasaki.