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One interesting topic that people like to research is the period between the World Wars, and how the United States evolved from an equal ally of Western Europe at the end of World War I to the Arsenal of Democracy in World War II. The U.S. Navy is a great example of how world events contracted and inflated the service as it was struggling to meet the demands of restrictive naval limitation treaties, while also protecting the United States and its far flung territories across the Atlantic and Pacific as an emerging global maritime power. Emerging from the Great War with budget cuts and surplus vessels, the Navy entered a period of innovation characterized by the development of new technology balanced by a “make do” mentality. They experimented with primitive aircraft carriers and early naval aircraft and made improvements on submarines, the definitive weapons of the next war.


The Office of the Secretary of the Navy was also influential in the management and protection of United States territorial holdings like Puerto Rico, the Virgin Islands in the Atlantic, and Guam, Midway, Hawaiian Islands, and the Philippines in the Pacific. While maintaining the uncomfortable balance between budget cuts and the increasing threat of war in both oceans, the Office of the Secretary of the Navy shifted priorities from the build up of naval bases in these remote bases to planning the logistical framework of the next war.


A great resource for beginning research on the interwar U.S. Navy is with the General Correspondence of the Secretary of the Navy. The general correspondence includes letters, memoranda, and other reports from different parts of the Navy, including the assistant secretaries of the Navy, bureau heads, the Chief of Naval Operations, and the Judge Advocate General. The correspondence also includes letters to and from other parts of the government, including President Franklin D. Roosevelt and the U.S. Army.


The best starting point for accessing the correspondence is M1067: Name and Subject Index to the General Correspondence of the Office of the Secretary of the Navy, 1930-42. This series of index cards was originally microfilmed and made available in the microfilm room at the National Archives in Washington, DC. The microfilm has now been digitized and is available in the National Archives Catalog. This series consists of 187 rolls of microfilm listing names and subjects alphabetically. Each card relates to a name or subject, has a brief line about the letter, the date of the letter, and the Navy Filing Manual designation it is filed under.


Once you have the dates and Filing Manual designations from the microfilm series, you can use this information to search through the two general correspondence series: the General Files, 1926-40, or the General Correspondence, 1940-42. Both series are arranged according to the Navy Filing Manual.


Please note, the General Files series starts in 1926, but the index does not start until 1930. The Office of the Secretary of the Navy believed there would be no reason to index the correspondence following the publication of the Navy Filing Manual in 1925. By 1930, however, the Office had more correspondence than could be navigated with just the filing manual, and thus created an index. The division of the two series in 1940 corresponds to the beginning of World War II.


The two general correspondence series contains correspondence of the Office of the Secretary of the Navy at the unclassified and restricted levels. Even at these lower classification levels, there is a broad span of topics regarding the interwar period, ranging from new constructions to planning policies. There are also cards about companies and individuals that helped build up the fleet in the period before the war. The cards also include topics related to gender and race topics including developing policies on women and African Americans serving in the Navy or in the Naval Reserve. There are many interesting gems in these records such as the expansion of the U.S. Navy through the planned, appropriated, and constructed new ships before December 1941 at different naval shipyards. There are copies of the 1940 appropriation bill, better known as the “Two-Ocean Navy” bill or the Vinson-Walsh Act, which lists all the new ships of the expanding Navy that would later impact the outcome of the Second World War.


For those interested in the events in the Pacific Theater and the developments of advanced bases, there are index cards for islands including Midway, Wake, and the Hawaiian Islands, and what was being planned for the Asiatic Fleet based in the Philippines. There are also several cards regarding war plans and fleet exercises.


In addition to the General Correspondence of the Office of the Secretary of the Navy, there are also the Formerly Confidential and Secret Correspondence series of the Office of Secretary of the Navy. The 1927 to 1939 portion of the Formerly Confidential and Secret Correspondence share a single index. Although this index has not been digitized, it is similar in nature to M1067 in that it consists of name and subject index cards arranged alphabetically by topic. It is arranged in four parts: incoming correspondence, name and subject index, and outgoing correspondence are arranged alphabetically; and a second name and subject index is arranged according to  Navy Filing Manual designations. The name and subject portion of the index lists the topic and what correspondence is associated with it, what classification the correspondence is under, and what Navy Filing Manual designation it was given. Certainly, you can experiment with the Navy Filing Manual portion for the index too, and see what kinds of materials are under a particular Filing Manual designation.


The Formerly Confidential and Secret Correspondence are divided into two different series. Both series are arranged by the Navy Filing Manual. Since these correspondence series had been classified at a higher level, they should include more details on particular topics than the General Correspondence.


The Formerly Confidential and Secret Correspondence and indices for 1940 to 1947 dovetail to the earlier series.


The index to the later Formerly Security Classified Correspondence of the Secretary of the Navy and Chief of Naval Operations, 1940-47, is divided into several sub-sections by year blocks. Under each subsection, the index cards are divided into groups of incoming, outgoing, alphabetical by topic, and the Navy Filing Manual. The Formerly Security Classified Correspondence is divided into year blocks, then arranged by classification level, and then according to the Navy Filing Manual. You can explore the different formerly classified correspondence series by either using their respective index or utilizing the Navy Filing Manual designations.


In addition to the other correspondence series, the index and the general correspondence overlap with other microfilm collections of the Fleet Problems and the Records of the World Crisis, which have been discussion topics on the History Hub.


The correspondence series of the Office of the Secretary of the Navy from the interwar period to the early years of World War II illustrate the ebb and flow of national and naval policies in regards to international naval treaties, the shift from limiting naval construction to mass production into the expansion of the “Two Ocean Navy”, and from tentative budgeting for naval outposts to a mad rush to re-enforce them as the situation began to turn towards general war.


For information on the Index and the General Correspondence of the Office of the Secretary of the Navy, 1930-1942 and the Index and Formerly Confidential and Secret Correspondence of the Secretary of the Navy, 1927-39, please contact For questions about the Index and Formerly Security Classified Correspondence of the Secretary of the Navy, 1940-47, please contact


From a historian’s perspective, it’s easy to see how the stresses and strains between nations lead to the outbreak of war. But what about at the time? What was known? What was missed? President Franklin D. Roosevelt wanted answers to these questions, but who could he ask? Who were the proverbial weathermen that could forecast the typhoons that hurled the world into chaos?


President Roosevelt turned to Secretary of the Navy Frank Knox for answers. Roosevelt asked Knox to gather all the naval attaché reports and dispatches from key foreign cities going back to January 1937. He wanted the search to include reports and dispatches from London, Paris, Brussels, Rome, Berlin, Moscow, and Tokyo. The President asked for reports from Bulgaria and Austria too, but there were not any naval attachés there during the specified period.


The reports and dispatches were compiled into a series of records, which was later microfilmed as National Archives Publication M975: Selected Naval Attaché Reports Relating to the World Crisis, 1937-1943. It is a small three-reel collection.


The documents that were microfilmed are stamped with various classification markings from Secret to Restricted. These documents have been declassified under declassification authority - DECLASSIFIED, E.O. 11652, Sec. 3(E) and 5(D) or (E), NND 730043, and researchers may make copies of the documents.


The reports are arranged in two subseries: “Estimate of Potential Military Strength” and “Probability of an Outbreak of War.” They are further arranged by post of attaché, and thereunder chronologically and numbered consecutively. Letter symbols have been employed to identify the post from which the reports originated. The symbols used for the “Estimate of Potential Military Strength” are:


  1. London
  2. Paris
  3. Brussels
  4. Rome
  5. Berlin
  6. Moscow
  7. Tokyo

The symbols used for the “Probability of an Outbreak of War” subseries are:

  1. London
  2. Paris
  3. Brussels
  4. Rome
  5. Berlin
  6. Moscow
  7. Tokyo


There are several volumes of reports and dispatches for each city.


Preceding each group is a summary that includes excerpts and abstracts of the reports with letter and number notes written in the margins, which correspond to the report or dispatch that it was taken from. For example, K-2-77 indicates the 77th Report in the 2nd Volume from Rome (K) from the subseries “Probability of an Outbreak of War.” There is sometimes a number in parentheses indicating a page number from a report.


The information discussed in the reports varies from post to post. For example, the Berlin reports include U-Boat development and the success of overtaking parts of Czechoslovakia, the London reports cover the expansion of British Forces and preparations for shifting of power in Europe, and the Tokyo reports include strategic Japanese plans for China and the expansion of the Japanese military and naval forces.


These reports were a selection made by Secretary Knox, but more context can be found through further research. Record Group 38: Records of the Chief of Naval Operations includes  additional bodies of naval attaché intelligence reports both at the National Archives in Washington, DC (in Entry NM-63 98 for the period of 1900 to 1939) and the National Archives in College Park (in Entries A1 98-A and A1 98-B for the period of 1940 to 1946). The index to the naval attaché files at the National Archives in College Park has been microfilmed in NARA Publication M1332, which also has been digitized, and will be the subject of a future History Hub blog. In addition to the naval attaché reports, there are several series of monograph files relating to Germany, Japan, and other countries. The monograph files are basically the Office of Naval Intelligence’s vertical files, where articles, reports, and other printed material were collected and sorted into subjects like functions of the government, and army and navy of a particular country. Another resource is the two series of administrative files for the Office of Naval Intelligence (Entries UD 84 and A1 85), which have inclusive dates that start before the war, but the bulk dates are the war period. These administrative files are arranged according to the Navy Filing Manual (4th Edition, 1941).


Despite myriad signs, changes in the wind, and the scent of the coming storm, no one was able to predict what would spark World War II. The naval attachés knew about their individual areas, but could only make guesses as to what their future would hold. The storm would not arrive until the first drop of rain and the first rumble of thunder, which was no longer in the distance, but in the here and now.


In the aftermath of World War I with the rise of American global status, a colonial power in the Carribean and Pacific and a component of a European alliance with Great Britain and France, the United States Navy began to take their theories of fleet actions and developed them in practical real world exercises.  These practical exercises were known as the Fleet Problems conducted between 1923 and 1941.  The Fleet Problems were number I to XXI and there was a XXII Problem planned for January 1941, but it was cancelled.  These records were microfilmed into National Archives Publication M964: Records Relating to United States Navy Fleet Problems I to XXII, 1923-1941.


The records contained in this series come from three different record groups: Record Group 38: Records of the Chief of Naval Operations, Record Group 80: Records of the Department of the Navy, and Record Group 313: Records of Naval Operating Forces. In Record Group 38, these series are from Division Fleet Training, Confidential Correspondence, 1927-1941 and Confidential Reports, 1917-1941. In Record Group 80, there are documents from the Secretary of the Navy’s Secret and Confidential Correspondence, 1919-1926 and the Secretary of the Navy’s Confidential Correspondence, 1927-1939. And in Record Group 313, there is the Commander-in-Chief, US Fleet Confidential Correspondence, 1939-1940.


The Fleet components involved in the exercises were the Battle Force and Scouting Force. The Battle Force and Scouting Force were sub-divisions of the US Fleet that was reorganized in 1922. The Battle Force later was reorganized into the Pacific Fleet and the Scouting Force was reorganized into the Atlantic Fleet in 1941.


Each of the exercises were designed to address a specific component or scenario within the context of a “colored” war plan.  The opponents in the exercises were described as “Blue” forces, the United States, and aggressor forces “Black”, Germany, and “Orange”, Japan. The locations of the exercises do not necessarily reflect the hostile forces being tested in that there are a few Fleet Problems staged in the Caribbean simulating fleet actions around Hawaii. In some of the Fleet Problems, the Battle Force and the Scouting Force were pitted against one another, and in other cases a single force was divided into both opponents.


One of the more interesting aspects of the Fleet Problems is how the US Navy was preparing for the next war and how new equipment would be used like aircraft and submarines as well as new tactics like amphibious landings. Another factor that the US Navy was contending with is the possibility of a two-ocean war with a limited fleet that was constricted by the Washington Naval Treaty of 1920-1921.


Many naval historians look to the Fleet Problems as evidence to the axiom of “Generals are always prepared to fight the last war” or in this case “Admirals.”  The general consensus is that the Fleet Problems reinforced the notion that the next naval war would have the battleship as the centerpiece of a fleet at the exclusion of other vessels.  Other vessels like aircraft carriers and submarines were auxiliary to the fleet and would be only used in reconnaissance roles rather than a major projection of naval power.  Although, carrier-based aircraft proved to be very useful in turning the tide in a battle during the Fleet Problems. In the 1930s as a result of the Fleet Problems, the Navy elected to construct more aircraft carriers and expand naval aviation. But the true potential of aircraft carriers within a battle group had yet to be proven and would not until the Second World War.


On aircraft carriers, there were several tests of carrier based aircraft against naval bases such as the Panama Canal and more famously, Fleet Problem XIII in 1932 where the USS Saratoga (CV 3) successfully attacked the Naval Base at Pearl Harbor, HI in a test of the base’s defenses. 


For submarines, their potential as a weapon continued to be misunderstood and mired in world opinion, being compared to German U-boats. and being anchored to fleet reconnaissance. The term “Fleet Submarine” comes from this period when the Navy was trying to have submarines operate with the surface fleet and not be perceived as the lone wolves of the First World War preying on commercial shipping.  But because of the dramatic shift in speed on the surface compared to a submarine’s speed underwater, it was hard for the surface fleet to interact with submarines without planning submarine positions far in advance of the fleet. Another aspect of the Fleet Problems that showed bias against submarines was the criteria during exercises where submarines attacked escorted convoys.  Detection amounted to being successfully attacked and this bred a cautious submariner in the early days of World War II.


There are many related records to this series at the National Archives in Washington, DC and at the National Archives in College Park. 


The National Archives at Washington, DC - Textual Reference (RDT1), which you can email at, has custody of series in Record Group 38: Records of the Chief of Naval Operations, Record Group 80: Records of the Department of the Navy and Record Group 313: Records of Naval Operating Forces.


Specifically in RG 38, there are the correspondence series of the Chief of Naval Operations, arranged by the Navy Filing Manual, that include discussions of fleet development and training as well as war planning prior to 1941.


In RG 80, there are three series of interest: the 1930-42 General Correspondence of the Secretary of the Navy, (the index is on the Catalog), the Records of the General Board, and the Records of the Joint Army-Navy Board. The General Board was an advisory board of retired Fleet Admirals, and the series pertained to innovations in new ships, new tactics, and new strategies. These series have their own filing scheme based on a topic that is different from the Navy Filing Manual. The Joint Board records reviewed war planning and the development of base defense for Army and Navy installations, both domestic and abroad.


In RG 313, there are series of records relating to the individual forces: Battle Force and Scouting Force, and some of their subordinate commands such as commander, submarines and commander, aircraft.


The National Archives at College Park - Textual Reference (RDT2) has custody of only a few series in Record Group 38: Records of the Chief of Naval Operations and Record Group 313: Records of Naval Operating Forces that would relate to the Fleet Problems because the majority of the pre-World War II Navy Records are in the custody of the National Archives at Washington, DC - Textual Reference.


In RG 38, there is a collection of records relating to the Fleet Problems in the records of the Strategic War Plans Division in Entry A1 355. The date range of these records is from 1912 to 1946 and divided up into 12 sub-series.  In particular, Series II: Naval War College Instructional Materials, 1914-1941 and Series IX: Plans, Strategic Studies and Related Correspondence, 1939-1945 have materials related to the Fleet Problems.  In Series II, there are continuations on the fleet exercises and analysis of each of the opponents’ situations. In Series IX is a set of copies of the historical development of the war plans arranged chronologically.  


In RG 313, there is a series of files covering 1940 to 1942 and the transition of Commander-in-Chief, US Fleet (1940), combined with Commander-in-Chief, Pacific Fleet (February 1941), and the two commands being separated in December 1941 following the attack on Pearl Harbor. The series is the General Files and Serials of Commander-in-Chief, Pacific Fleet, 1940-1942. This series fills the gap between the CINCUS files located at the National Archives in Washington, DC and the Commander-in-Chief, US Fleet (renamed COMINCH) Formerly Security-Classified Correspondence, 1942-1945 at the National Archives in College Park, MD. 


To inquire about the availability of related records that were suggested, please contact the National Archives at College Park - Textual Reference (RDT2) via email, If you are interested in ordering a copy, please provide your mailing address and phone number in your request since both are required for the reproduction order form.


To highlight another series that is available on the National Archives Catalog, we are featuring the new scanned series of index cards to the Anti-Submarine Incident Reports from the Anti-Submarine War (ASW) Section of the Records of the 10th Fleet in the Records of the Chief of Naval Operations (Record Group 38). 


Like many records at the National Archives, accessing the ASW Incident Reports has been a two-step process by reviewing the index and then ordering the reports.  The Incident Reports are arranged by report number, which is numeric and does not indicate the target, attacker, or date.  Because of this, the index is the only way to access them.  The index is arranged by the designation of the attacker of the enemy submarines.  On each card for an attacker, the incidents are arranged by date with a report number listed. 


To further explain the arrangement of the index cards, the four small boxes are divided into Ships (A-Z), US Naval Aviation, Non-Navy Aviation (Army, Marine Corps, Coast Guard), Foriegn Aviation, and a few cards on Surrendered Vessels.


The reports themselves are a record of an attack on an enemy submarine usually German U-boats and some Japanese submarines. These reports detail how contact was made, how the attacking unit proceeded to pursue the enemy, the attack itself, and the assumed result of the attack. The purpose of the reports and the collection as a whole was to learn how to improve anti-submarine strategies and tactics by seeing what worked and what did not.


Due to the lack of organization and a central channel for reporting incidents at the beginning of the war, anti-submarine incident reports were not consistent until mid-1942. As the United States entered World War II, America was confronted by a clear and present threat of German and Japanese submarines attacking our supply lines with Great Britain and Australia as well as moving our own troops and equipment to the battle fronts across the sea. Despite this threat, the US  was slow to adopt anti-submarine methods like convoying, securing information on departing ships at ports, and even blacking out coastal cities so as not to silhouette incoming and outgoing ships.  


The first move to addressing the submarine threat was the formation of the Convoy and Routing Division under the Chief of Naval Operations in May 1942.  The Convoy and Routing Division was responsible for routing and protecting merchant shipping in U. S. waters and troopships going abroad. C and R was the forerunner to the 10th Fleet, which was established in May 1943. In the year between the establishment of the two commands, the science of anti-submarine warfare had blossomed with refinements to SONAR, improved depth charges, and forward throwing subsurface weapons called Hedgehogs. Also, there was improvement to aviation with multi-engine aircraft that could take air patrols out further into the U-boat infested waters of the Atlantic and with new Arc lights to illuminate them in the night as they recharged their batteries on the surface following a day’s hunting.


Around April-May 1942, the reporting on anti-submarine activity became more regular and consistent.


The index cards and the ASW Incident Reports also relate to other series in the Records of the Chief of Naval Operations (Record Group 38). The Incident Reports, in some cases, may duplicate what are in the Action Reports and in other cases, they are purely unique. The detail also varies widely from a single page or less description to a multi-page report complete with sketches of the attack. Therefore, if you are researching anti-submarine operations during the war, it is important to review both the Action Reports and the ASW Incident Reports.


These series also relate to other records within the Records of the 10th Fleet such as Convoy Reports and US and Allied Shipping Losses as well as the separate series of Armed Guard Files, which are reports from the US Naval Armed Guard units that served aboard merchant ships to defend them.


Another series of records that have records relating to Anti-Submarine Warfare during World War II are the World War II Command Files.  This series is arranged hierarchically by command and office.  For example, there are ASW bulletins among the files of the Commander-in-Chief, US Fleet (COMINCH/CINCUS); ASW Information (weekly notices) filed with the records of the Atlantic Fleet; and separate sections of records for the offices of the Anti-Submarine Section and the 10th Fleet that were directly related to ASW efforts during the war. There may be other ASW-related materials incorporated into a larger report sent to a higher fleet or regional command such as an island command, sea frontier or naval district.


To inquire about the availability of an Anti-Submarine Incident Report or any of the records suggested, please contact the National Archives at College Park - Textual Reference (RDT2) via email, If you are interested in ordering a copy, please provide your mailing address and phone number in your request, which is required for the reproduction order form.


To continue to highlight new digital series available on the National Archives Catalog, World War II War Diaries, Other Operational Records and Histories, 1942-1946 is another series that has come from NARA’s digital partners. This series includes some war diaries, some action reports, some submarine patrol reports and some battle histories of various naval, Marine, and other Allied commands during World War II. These records were scanned from a microfilm series that the Navy created from select war diaries and other reports.


This series is the first step in researching a Naval and some Marine operations during World War II, but remember this is not a comprehensive series of war diaries and so its title is a little misleading.  If you cannot find a war diary or an operational report for the Naval command you are interested in the digitized war diary series, then please be aware that there are larger textual series of War Diaries, Action and Other Operational Reports, World War II Command Files in the Records of the Chief of Naval Operations (Record Group 38) and the U.S. Marine Corps Operations in World War II (a. k. a. Geographic Files) in the Records of the US Marine Corps (Record Group 127) where you might find what you are looking for. 


One of the interesting tricks to the textual series of war diaries is that there are some command war diaries that have been stamped saying that a certain portion of the war diary has been microfilmed. Those microfilmed portions can be found in this series.  As a follow-up to this statement, please do not assume that in all cases where one series ends the other begins. There are several cases where there is duplication and in others there are exclusively solitary copies of reports - meaning they exist solely in one series and not in the other. 


The duplication of reports in multiple series or the isolation of unique reports in individual series can be said for action and other operational reports.  Again If you cannot find a particular action report or Marine operational report, then you might try to look at the associated textual record series.

If you need to check for the availability of a war diary, action report, or another type of operational report, then please contact the National Archives at College Park - Textual Reference (RDT2) via email, and RDT2 can check their holdings.  If you are interested in getting a copy, then please provide your mailing address and phone number in your request in case RDT2 needs to draft a reproduction order form for you.

In the last few years, the National Archives has been partnering with online services like and to digitize microfilm and microfiche series of records. The intent was that after a span of time on these sites, these materials eventually will be made available on our Catalog. One of these series is the World War II Submarine War Patrol Reports, NARA Publication M1752, NAID 305243, and Entry A1 307 in Record Group 38: Records of the Chief of Naval Operations.


This series is arranged by the name of the submarine and then by war patrol number, but through the Catalog, you can “Search Within This Series” and search for any specific submarine.


Please remember, this series only includes reports of assigned war patrols and war patrols that were completed. The majority of the war patrol reports are from submarines assigned to Commander, Submarine Forces, Pacific; Commander, Submarine Forces, Southwest Pacific; and Commander, Submarine Forces, 7th Fleet. If you are looking for periods of training, extra duties outside of a patrol, or when a submarine was lost, then you will need to look in other records in Record Group 38: Records of the Chief of Naval Operations or in Record Group 313: Records of Naval Operating Forces.


At the beginning of World War II, Chief of Naval Operations and Commander-in-Chief, US Fleet decided that submarines operating in the Pacific were not to maintain war diaries like other vessels, but to file report on their assigned war patrols as an equivalent record of activity.


The war patrol reports consist of several sections including a brief summary of events between patrols, which covers training and overhauls, a chronology of patrol, a record of sightings (ships and aircraft), data on torpedo firing, and evaluations of different departments and sections aboard the boat on how equipment and crew performed during the patrol.


These records and this digital collection is helpful to begin any research on World War II Submarine Operations in the Pacific. During the war, submarines were asked to do more than sinking ships.  They were asked to drop off or pick up troops like in the Makin Island Raid and the invasion of Adak, rescue downed pilots in lifeguarding missions, photo-reconnaissance missions, evacuating people and material, and to lay mines.  Sometimes there were additional reports that were filed, but not included in the war patrol reports.  These additional reports can sometimes be found in the World War II Action and Operational Reports, Entry A1 351 in Record Group 38: Records of the Chief of Naval Operations, NAID 305236.  The action reports can also include reports on the loss of a submarine, collecting all the available information on when they were last hear from or seen.


There are other series within Record Group 313: Records of Naval Operating Forces under Commander-in-Chief, Pacific Fleet, Commander, Submarine Forces, Pacific and Commander, Submarine Forces, Southwest Pacific. There are several entries for these commands within this record group.  These series are the administrative files of these commands and are arranged by or use the Navy Filing Manual (4th Edition, 1941). You can use these files to further develop the background to a mission or what information was gained from a mission.