I don't like Robert McNamara, circa 1966. (I was in Vietnam at the time.) I think his overly analytic approach to warmaking contributed greatly to the Vietnam quagmire-fiasco. But I do appreciate the Robert McNamara who assisted U.S. Army Air Force General Curtis LeMay at the outset of World War II. To grossly oversimplify, LeMay didn't know how many planes he had or where they were. McNamara came aboard and fixed that. After the war, McNamara was one of the handful of "Whiz Kids" who brought Ford into the modern world by, in effect, doing the same thing for Henry Ford that he had done earlier for General LeMay.
Robert McNamara and Peter Drucker "arrived on the scene" at roughly the same time. And faced an/the same intriguing issue. In short, whether the military or big corporations, organizational size and complexity had far outstripped the toolkit available to manage these busting-out-of-their-pants behemoths.
Jack Welch was not the first CEO of GE, though to read Fortune in the '90s one might have thought so. And Peter Drucker didn't "invent" management. The Chinese probably did thousands of years ago—among other things, Sun Tzu's roughly 2,500-year-old The Art of War is a full-blown "management" text. So, too, Machiavelli's The Prince. And Frederick Taylor's century-old The Principles of Scientific Management.
But Peter Drucker did arguably (1) "invent" modern management as we now think of it; (2) give the study and craft of management-as-profession credibility and visibility, even though biz schools like Harvard had been around for a long time; and (3) provide a (the first?) comprehensive toolkit-framework for addressing and even mastering the problems of emergent enterprise complexity.
And he did something else incredibly important: He popularized the study of-appreciation of modern management. Doubtless Mr Drucker would have been appalled to be described as a "popularizer"—after all, that was one of his abiding and biting criticisms of me. But the truth is that, though his consulting was carried out in the stratospheric confines of CEO-world, his books and articles were very comprehensible and accessible to the likes of LTJG Thomas J Peters, USN, in 1968, when Peters, age 25, left Vietnam and was assigned to a forces management team in the Pentagon. No, the Stanford Graduate School of Business from which Peters got an MBA six years later, in 1972, did not assign as much as a single word of Drucker's work. But in 1968 Peters read (devoured!) his first management text, Drucker's The Effective Executive—and was profoundly influenced by it. LTJG Peters was hardly alone!
To be sure, Drucker wrote continuously on a variety of issues; he was a genuine polymath. His comprehensive pieces in the Atlantic, for instance, covered an absurdly wide spectrum of human endeavor. Yet Drucker, correctly, will not be known for that work, and personally I don't think his historical significance will hinge on "inventing" the "knowledge worker." Rather, it will rest on works such as The Concept of the Corporation (1946), The Practice of Management (1954) and The Effective Executive (1967), which are the tracts that launched the "practice of management" as we know it to this day—and probably as we will know it for decades to come.