For the Common Defense by Allan R. Millett and Peter Maslowski

A concise, yet excellent, overview of American military history from 1607 through Desert Storm.

US Army Counterinsurgency and Contingency Operations Doctrine, 1860-1941

and

U.S. Army Counterinsurgency and Contingency Operations Doctrine, 1942-1976.

Both by Andrew J. Birtle

How “big” Army has dealt with the many small wars it has fought since the Civil War and how the soldiers involved not only fought but often found themselves in roles as governors, constables, judges, diplomats, explorers, colonizers, educators, administrators, engineers, and more. Birtle basically points out that while the Army continually devotes most of its planning and training to “big” war it has actually spent most of its time involved in “small” wars.