I am in the process of creating a more in-depth research guide for Military History. Several libraries have already done this, highlighting resources at their institutions. I have included these links below. Please keep in mind that we do not own or subscribe to the same resources, but we might have some of them! So if something looks useful or interesting to you, let me know and I can investigate further how to obtain these resources for you.
Importantly, these guides contain suggestions for books and also links to numerous primary source collections!