World War II War Diaries were compiled between about January 1, 1942, and about June 1, 1946, by the U.S. Navy, documenting the period from about September 1, 1939, to about May 30, 1946. They were identified by the Navy as "the principal means by which the day-to-day experience of the Navy is recorded for current study and future historical use."

The documents are arranged in two subseries: war diaries and other documents and an "index" (or register). Both subseries are arranged numerically by "microserial" number. They are further explained in the Archival Research Catalog (ARC) of the National Archives:

This first subseries consists primarily of daily operational journals (commonly referred to as war diaries) created by various naval commands, shore installations, ships and other activities throughout the Navy, as well as some Marine Corps commands. Most war diaries provided a day-to-day record of operational activities and sometimes administrative activities as well. War diaries were submitted by most units in the Navy, and most of the Marine Corps war diaries were submitted by aviation units such as fighter squadrons.

The quality of the diaries varied widely, with some providing detailed accounts, while other diaries contain only cursory information. For example, war diaries of some Naval Operating Bases (NOB) indicate what vessels were present or which vessels entered or departed the base on particular days, while others do not contain that information. Generally, higher level commands, commands that encompassed large geographic areas (such as naval districts), and large ships (such as aircraft carriers and battleships) submitted the most detailed war diaries. War diaries of smaller units and ships often provide less information.

Interspersed among the war diaries are a number of action reports submitted by various Navy ships, units and commands, providing narrative accounts of warfare operations against enemy forces as well as details of damage sustained in battle ("war damage reports"). Also interspersed among the war diaries are a number of submarine patrol reports providing details of missions undertaken by American underwater forces, as well as a number of "war histories," narrative accounts describing the activities of a particular ship, station or command during the war.

The first subseries also contains British Admiralty (naval headquarters) war diaries from the outbreak of war in Europe in September 1939 to the fall of 1945, and signals (radio communication) documentation relating to the evacuation of British and French forces from Dunkirk, France, during late May-early June 1940. There are also compiled reports on various small-scale surrenders of Japanese forces scattered around the Pacific Theater of Operations during the fall of 1945.

The second subseries consists of an "index," or register, consisting of lists indicating what documents are contained on each reel of microfilm. Information in the index includes each document's microserial number, its creator (ship, unit or command), the type of document (such as war diary, action report, or war history), the creator's filing classification and document serial number, the dates covered by the content of the document, and the date the document was created.

When browsing for a particular ship, you may find it under its name or under its name as USS, or in both places. As an example, war diaries for the USS Tippecanoe can be found under "T" for Tippecanoe, and under "U" for USS Tippecanoe. Remember to look in both locations, as well as perform a search on the vessel name in case it is mentioned in reports and diaries of other naval units.

Sections of each war patrol report include the following:

A) Prologue
B) Narrative
C) Weather
D) Tidal information
E) Navigational aids
F) Ship contacts
G) Aircraft contacts
H) Attack data
I) Mines
J) Anti-submarine measures and evasion tactics
K) Major defects and damage
L) Radio
M) Radar
N) Sound gear and sound conditions
O) Density layers
P) Health, food, and habitability
Q) Personnel
R) Miles steamed - fuel used
S) Duration
T) Factors of endurance remaining
U) Remarks

Military designations are an alphabet-soup mix of acronyms and abbreviations. The hierarchical descriptions for the World War II War Diaries include many such combinations of letters. Among them are:

CGAS – Coast Guard Air Station
CGC – Coast Guard Cutter
CINCPAC – Commander in Chief, US Pacific Fleet
COMDESRON - Commander Destroyer Squadron
CTF – Central Task Force
CTG – Commander Task Group
CTU – Commander Task Unit
DesDiv – Destroyer Division
LCI – Landing Craft, Infantry
LCI(L) – Landing Craft, Infantry, Large
LST – Landing Ship, Tank
LT – Large Tug, Army
MTB – Motor Torpedo Boat
MTBRon – Motor Torpedo Boat Squadron
NSB – Navy Submarine Base
NSD – Naval Supply Depot
NYd – Naval Yard
ONI – Office of Naval Intelligence
PhibFor – Amphibious Force
TorpRon – Torpedo Squadron
USS PC – US Ship, Patrol Vessel, Submarine Chaser (173’)
USS SC – US Ship, Submarine Chaser (110’)
UtRon – Utility Squadron
YMS – District Motor Mine Sweeper
VB – Navy bombing plane, or Navy dive bomber squadron
VF – Navy fighter plane, or Navy fighter squadron
VGF – Escort-fighting squadron
VGS – Escort-scouting squadron
VMF – Marine fighter squadrons
VMJ – Marine utility squadron
VMSB – Marine scout bombing squadron
VMTB – Marine torpedo bomber squadron
VS – Scouting plane
VT – Torpedo plane, or Navy torpedo bomber squadron
YMS – District Motor Mine Sweeper
YP – District Patrol Vessel

More can be found on the U.S. Navy Abbreviations webpage at the Navy History & Heritage Command.

From the following Fold3 title page you can search, browse, and see what others are finding within these documents:

WWII War Diaries

These images are digitized from 2,199 rolls of microfilm. They were originally textual records comprising 114 linear feet. They are archived in Archives II, the National Archives at College Park, Maryland.

As these documents were microfilmed, they were assigned an arbitrary sequential "microserial" number and were not filmed in strict chronological order.

More information is available through the Archival Research Catalog (ARC).