However, at Pearl Harbor the resilience of the American Standard-type battleship to survive damage was demonstrated, but they would have been loss in open seas. Although all eight American battleships were hit and damaged and four were sunk, it was possible to return six of the ships back into service, due to they were in a shallow water. "Arizona" was lost due to a catastrophic explosion of her magazine spaces. Competing theories exist as to how this occurred, but ultimately no practical thickness of deck armor could protect any battleship from a vertical bombing attack.