"War Is A Racket" by Major General Smedley Butler
He wrote this book in 1935 and it is as brilliant in in its analysis as it is surprising in its source. A few quotes that caught my eye on an initial read:
These are just some snippets. I highly recommend reading the whole piece. It is not a long read, only 14 pages. But along with Eisenhower's warning of the dangers of the Military-Industrial Complex in his farewell address, this may be the most astounding and astute warning ever issued by a high ranking US military man.