The library catalog and WorldCat use Library of Congress Subject Headings. The list of authorized subject headings is available online from the Library of Congress Classification/Subject Headings database. However, you can also start with keyword searches to gather some relevant titles, then look at their subject headings to discover the official terms to use.
Here are some subject headings related to the Spanish Civil War & Revolution:
Spain -- History -- Civil War, 1936-1939
Alcazar (Toledo, Spain) -- Seige, 1936
Other related headings:
Fascism -- Spain
Francoism
Spain -- Politics and government -- 1931-1939
Spain -- Foreign relations
Although Randall Library does not have books listed in the catalog under these headings, you will find them in WorldCat (and perhaps in other databases using LC Subject Headings:
Brunete, Battle of, Brunete, Spain, 1937
Ebro River, Battle of the, Spain, 1937
Guadalajara, Battle of, Brihuega, Spain, 1937
Madrid (Spain) -- History -- Seige, 1936-1939
Pozoblanco, Battle of, Pozoblanco, Spain, 1937
Teruel, Battle of, Teruel, Spain, 1937-1938
Valencia, Battle of, Spain, 1938
More on Subject Searching:
Libraries and database creators try to structure language in a way to make browsable lists. Subject terms tend to be set up in a hierarchical manner. The Spanish Civil War is an excellent example of this principle. To understand this better, try a Keyword search in the Randall Library Catalog for "Spanish Civil War" Then, do a Subject search on "Spain History Civil War." Notice that you retrieve more items using the later term, because it is the "official" indexing method. This structure allows you to browse through results for all periods of the history of Spain, and retrieves materials even if they do not include the phrase "Spanish Civil War."
Just because an item's subject heading does not include "History" as a subdivision does not mean it has no history in it. In particular, look at the publication date. It may be a source contemporary to the period, i. e., a primary source.
Even if you are doing a keyword search, using phrases from the subject headings typically improves the relevance of your results.
Also consider keyword searches on personal names relevant to the Spanish Civil War. Typically, names are entered with the last name first, e.g., Franco, Francisco. Do both Author and Subject searches to find books by and about the individual