Naval enlistments during the First World War totalled 407,360. Many of these individuals served as officers or ratings in the world's strongest maritime force, the Royal Navy. The service records of ratings who joined the Royal Navy as regular servicemen between 1873 and 1923 are listed in The National Archives' ADM 188 series. They contain basic biographical information and are arranged in the catalogue by service number - see, for example, the record for James Henry Dellbridge. For further information, see our guide to Royal Navy ratings.

The microfilmed service records of Royal Navy officers in ADM 196 are divided into two series, for executive officers and warrant officers respectively. These records usually provide basic information about an officer's personal life (date of birth, name of wife, name and profession of father) and more detailed accounts of his career with the Royal Navy (dates of commissions and promotions, details of honours, and dates of appointment and discharge from each ship served). In addition, there are several series of confidential reports that briefly summarise an individual's suitability for promotion.

There is no overall name index for the ADM 196 records, and in some cases, it is necessary to trawl the service records by date. The date on which a particular officer joined the Royal Navy, as well as dates of his promotions, can be found in the alphabetical list of officers in the Navy List (available at The National Archives). For further information, see our guide to Royal Navy officers’ service records.

Not all First World War naval servicemen and officers served at sea. The Royal Naval Division (RND) was formed in 1914 out of 30,000 sailors for whom the Royal Navy had no ships. Initially under Admiralty control, until it was incorporated into the army in 1916 as the 63rd (Royal Naval) Division, the RND fought on the Western Front and in Gallipoli.

Its surviving service records are listed in the ADM 339 catalogue, where they are divided into three alphabetically indexed categories for officers, ratings, and men discharged dead (both officers and ratings). Records of most RND officers can also be found in WO 339.

The Admiralty drew heavily on its reserve ranks during the war. First created in 1859, the Royal Naval Reserve (RNR) was a body of up to 30,000 merchant seamen and fishermen on whom the Royal Navy called in times of national crisis.

The service records of RNR officers who served between 1910 and 1920 can be found at The National Archives in the ADM 240 series, arranged in order of date of commission. Additional information about service may be found in the files and record-of-service cards in series ADM 340. Service records for ratings are held on microfiche in the BT 377 series. These are accompanied by two sets of name indexes that enable the reader to find the individual record of a rating via his service number. For further information, see our guide to Royal Naval Reserve personnel.

Royal Naval Volunteer Reserve

The National Archives also houses the surviving registers of service for seamen employed in the Merchant Navy during the war. Most of the records for the 1913-18 period were apparently destroyed in 1969. Information about merchant seamen discharged between 1918 and 1921, however, can be found in the alphabetically listed CR10 card indexes in BT 350.