Not finding a book on a particular subject or historical event? Broaden your search. For example, if a search for "Battle of Metz" yields no results, try the following search:
World War II AND (battle OR combat)
Tip #1: Think of as many synonyms and related terms as possible for your topic. Authors may use different words to describe similar ideas, so searching with multiple keywords will ensure that you do not miss out on relevant material just because it employs different terms.
Tip #2: For quick, effective searching, utilize Boolean operators.