7 December 1941
On the morning of 7 December 1941 USS Oglala, flagship of the Pacific Fleet Mine Force, was tied up outboard of the light cruiser Helena (CL-50). They were alongside Pier 1010 at the Pearl Harbor Navy Yard, with an eight-foot floating cushion (camel) between them. Japanese torpedo planes of the first attack wave hit the cruiser with a single torpedo, which ran under Oglala to hit Helena's starboard side. The torpedo's explosion broke through the minelayer's port bilge amidships, and she rapidly took on water. A bomb that burst nearby caused further damage. With the marginal watertight integrity typical of older ships, Oglala's flooding could not be contained.
When it became clear that she might sink, Oglala was moved aft of Helena, so she would not pin the warship against the dock. About two hours after receiving her initial damage, she rolled over to port and sank beside 1010 dock. There Oglala became the object of a prolonged, and ultimately successful salvage effort.
Read more about this topic: USS Oglala (CM-4)