My work has lead me to these two related sources. They can be hard to find sometimes, so here is a quick guide.
First is the Combined Arms Research Library (Fort Leavenworth's Library) Digital Library. It includes a variety of publications and primary documents that might be useful. For example, here is Wesley Clark's 1975 Master's Thesis from the Commmand and General Staff College.
A more hidden source, but also excellent, is the Center for Army Lessons Learned Public Archives. The webpage is here, but if that does not work, this is how you get to it: Go to the homepage for Military Review, and click on "Past Editions" in the sidebar on the left. There you will find an unwieldy menu system that has all of the theses and monographs from the Commmand and General Staff College and School of Advanced Military Studies since 1964, a number of primary documents and other publications, and full texts of the publication Military Review since 1922. Why is that good? The early editions were literally a review of military literature. But in 1933, they started including original studies by Army officers. So say you wanted to see what future World War II Corps commander, Army Chief of Staff, and Ambassador to Vietnam J. Lawton Collins had to say about "The Conduct of a Holding Attack" in 1933 when he was a lowly major, you could look it up and come up with this:
Or what did instructor of tactics at Fort Leavenworth and future division, corps, and army commander Major Manton Eddy say in 1935 about World War I tactics?:
Or what did future Air Corps and Air Force General Lewis Brereton write in 1939 about the application of airpower?:
It's all yours. Enjoy.