Annual Reports of the Secretary of War
Annual Reports of the Secretary of War – http://catalog.hathitrust.org/Record/000078451
Representative questions that can be answered with this resource:
- How did US authorities deal with an outbreak of Bubonic Plague in Manila in 1899?
- How many US soldiers were there in China in 1923?
- Where can I locate specifications and test results for late 19th weapons such as the Skoda 5-Pounder Rabid-Fire Gun?
Spanning from 1863 – 1949, these reports cover a variety of topics. Sometimes they have details about conflicts the United States was engaged in at the time. For example, volume one, part 10 of the 1900 report (http://hdl.handle.net/2027/uc1.b2980393) provides a US view of civil affairs under its occupation government in the Philippines.
Sometimes they cover other matters. For example, the 1923 report (http://hdl.handle.net/2027/mdp.39015024071535) concerned itself chiefly with the economics of national defense and included comparisons of US military spending to those of other countries.
Nearly all of the annual reports will have statistics on the size, composition, and rough deployment of the armed forces. Most years also have an helpful index that might generate story ideas, such as the Bubonic Plague outbreak detailed in the 1900 report. The volumes from Hathitrust are also fully searchable.
In the digitized copies linked here, there is a gap from 1941 to 1947. As of this writing, I’m unsure whether this means the volumes were not published or simply not digitized.