Robert S. McNamara has been responsible for some very sweeping changes in the makeup and function of the Department of Defense. Not since the days when ""Engine Charlie"" Wilson was commenting on bird dogs and what was good for General Motors, has Defense received such controversial news coverage, yet, McNamara's program is not an easy one to grasp and explain. Thus Mr. Kaufmann's work fills a very definite need, and in order to do so has had to surmount some particularly formidable hurdles. McNamara's ""revolution"" has been two-fold; inheriting a system which was for all practical purposes wholly devoted to the concept of massive retaliation, he has attempted to convert it into one capable of ""flexible response"" to all various types and sizes of aggression; and he has introduced a great many procedural reforms within the structure of the Pentagon itself. It is not necessarily a criticism to note that Mr. Kaufmann is almost completely committed to the opinions of McNamara and the man to whose memory the book is dedicated, John F. Kennedy --- since the purpose here is to present their case, not to assess it. Coward this end he has wisely employed the Secretary's own statements wherever possible since ""McNamara is well able to speak for himself."" Another virtue here is the skill with which intensely technical matters have been explained.