It is possible that one of your ancestors or relatives was an officer in the Latvian army during the interwar period. If so, you have the opportunity to learn about their military service records in the files available online.
I usually start searching for officer files by looking up the officer's surname in Jānis Melderis' register "The Fates of 6,000 Latvian Officers During the Years of World War II."
The document in PDF format is available on the Latvian Officers' Association website.
In this table, you will find a number of important data:
Name, surname, and father's name.
Date and place of birth.
Date and place of death, if known.
The last officer rank in the Latvian army.
The next column describes the last position in the Latvian army and the further fate, as far as it has been possible to ascertain. The list contains many abbreviations, but they are all explained at the beginning of the document (starting from p.6.)
The last column contains sources of information. Firstly, there is the Latvian State Historical Archives Fund No. 5601 – the Army Staff Personnel Files Collection. In this example, the first entry about Kārlis Ādamsons, the number "1-53" in the last column denotes fund 5601, description 1, file 53 (5601-1-53), and this file can be found online.
The last column also contains many abbreviations. Each number in square brackets denotes some source of information - a book, publication in the press, archive document. What each number denotes can be found at the end of the document on p.548.
The most extensive source of information is the officer's file from fund 5601, and you can search for it online.
Go to the Familysearch.org website, log in through your profile, and search for this number (for example, the already mentioned Ādamsons case 5601-1-53) through Search>Keyword:
A list of several collections will open. Choose Latvia, Army Staff Records.
Continue searching for your file number in the collection. It's not so simple, as the documents are sometimes not organized in order. Some case numbers are written as 5601-1-53, while others are separately noted as 1/5/5601 (which refers to case 5601-1-5).
The first pages usually contain a summary with all the most important information, which may vary slightly in different files, but generally, it is as follows:
Service position
Awards
Birth data
Residence or to which parish registered
Faith
Education, both general and military
Marital status
Properties
Service career. Since many Latvian Army officers were educated and served already during the tsarist times, the service career also shows detailed information about this period.
The files of the older officers are very extensive, but much of the information repeats. For those officers who only graduated from the War School during the interwar period, the files are much shorter.
Some files also contain a photo of the officer.
The newest files are typewritten and in Latvian, but some documents may also be in Russian and handwritten.
Unfortunately, the information in the officers' files ends with the 1940s, and further fate can then only be sought in the table mentioned above by Jānis Melders and his mentioned sources.
I hope you succeed in discovering the fates of your family's officers!