Modern Military Records are those records created after 1900 and include all branches of the War Department, now the Dept. Of Defense.  These records are located in College Park Maryland at “Archives II”   If you want to know anything about the battles a relative fought in after 1900 this is the place to go.   You can hire researchers that will perform the research for you, though some are pricey.  I will have a list of researchers eventually.