A war diary is a regularly updated official record kept by military units of their activities during wartime.
War diaries are focused on the administration and operations of the unit they cover, but may also contain information about individual personnel.
All significant military actions, relocations, important messages and orders, casualties, material losses, reinforcements etc.
[4] World War II War Diaries from units of the US Navy (including all ships) and Marine Corps were declassified on December 31, 2012 by the Office of the Chief of Naval Operations (OCNO) and made available to the public through the National Archives and Records Administration (NARA).
These war diaries are part of a larger collection of records from the OCNO at NARA, currently spanning 1875 to 2006.