It was a bright, warm Hawaiian morning on 31 December 1941, when Admiral Chester W. Nimitz stepped aboard the submarine USS Grayling, moored in Pearl Harbor, for a brief 1000 ceremony in which he would assume command of the US Pacific Fleet, relieving Vice Adm. William S. Pye of the position after the 7 December attack there. But, throughout the area, the mood was anything but bright.