2012 George C. Marshall Lecture in Military History, and as one would expect from Bacevich, it was scathing, insightful, and a joy to read.
I would strongly recommend you simply click on the link above and read his comments, titled "The Revisionist Imperative: Rethinking Twentieth Century Wars." They are well worth the time. But for the sake of the discussion here, let me give the very brief summary: Bacevich argues that the US drew the wrong lessons from the 20th century because we look at the wrong bit of history. We focus major attention on the Second World War, and conclude that massive applications of American military power can defeat tyranny and restore justice. While Bacevich quibbles somewhat with this interpretation of World War II, his larger argument is that we forget lots of history which teaches different lessons.
I'd like to suggest that greater knowledge of the period prior to America's entry into the war might lend lessons which better suit the present day. America had only a limited presence in the wider world, much of it characterized by businessmen, journalists, and diplomats. Our power was far short of omnipotent. What could we do in Manchuria or Sudetenland? Very little.
This situation is well attested in that most popular of media: Hollywood. Think of Rick in Casablanca or, more recently, Mr. Jackson in The White Countess. From watching films such as these - rather than The Sands of Iwo Jima or the like - one learns that Americans are in constant danger of being overwhelmed by the complexity of foreign locales and the pace of events that happen there. Our American protagonists are not powerless to effect change, but their power is considerably circumscribed by events beyond their control. Moreover, men like Rick and Mr. Jackson bring about change only rarely through the power of the gun; more often their American dollars or their intimate knowledge of local cultures and politics carried the day.
A foreign policy based on this set of historical memories - rather than on the Second World War - would not simply retreat from the world, but would choose its battles wisely. It would not abolish the use of military force, but rather than seeking to build fleets of aircraft, it would focus on diplomacy, intelligence, and the application of soft power, particularly through NGOs and businesses. It strikes me as precisely the kind of foreign policy the present age demands.