Albert Einstein once observed that doing the same thing repeatedly and expecting a different result is a definition of folly. As the West's invasion of Afghanistan approaches its bitter conclusion, Einstein might well have been referring to our preferred military strategy for the past half-century.
Four times American-led armies have invaded and occupied foreign countries, and four times the model has failed, in Vietnam, Iraq (twice) and Afghanistan. Given that evidence, it seems that Western military staffs and academies have been fortresses of obsolete ideas rather than agents of strategic innovation.
Presumably, once the dust has settled after Afghanistan, Australia's political and military leaders will review our national defence strategy. Former US defence secretary Robert Gates may have inadvertently identified the essential start-point for any such review in his new book, Duty: Memoirs of a Secretary at War, in which he notes disapprovingly that President Barack Obama ''came to distrust'' his army, its commanders, and its strategy.
Notwithstanding Gates' censure, Obama seems to have a point: Afghanistan has, after all, been a political, economic, military, and social disaster.
The central question those responsible must answer is this: why has the West persisted in invading and occupying foreign territories as its preferred military strategy for 50 years when, as the evidence clearly shows, the model is broken?
The failure of contemporary Western strategic thought has two main causes.
First, simply put, the era has gone in which predominantly white, predominantly European, predominantly Christian armies could stampede around the world invading countries their governments either don't like or wanted to change. In the global village of the 21st century, that kind of mentality is obsolete.
Countries and interest groups connected by instant communications, travel, trade, finance, and shared individual (as opposed to national) interests no longer accept the assumption of Western superiority that shaped the preceding 500 years of the international order. Today, our ''expeditionary war'' is someone else's ''invasion''. The shift in terminology is both instructive and profound.
Second, the subjects of occupation have learnt how to exact costs that are too high for liberal-democratic societies to bear in situations that do not represent a threat to their national survival. The kinds of casualty rates accepted so carelessly by British, French, and German generals in World War I would be intolerable today. Thus, while US-led armies might not have been defeated on the battlefield in the traditional sense in Vietnam, Iraq, and Afghanistan, as body bags continued to be sent home, they were conclusively defeated on the field of public opinion.
Simultaneously, the economics of occupation have become an own goal for invaders. No Western general can credibly explain why the most technologically advanced armies the world has ever known should have to spend hundreds of millions of dollars trying (unsuccessfully) to counter improvised explosive devices - that is, cheap, home-made bombs used by socially primitive opponents.
To put it another way, in each of those ''expeditionary'' wars, the West's apparently technologically and sociologically inferior opponents have been able to define the nature of the fighting, a situation that seems to defy logic - well, habitual military logic, anyway.
Strategy must be the start-point for any analysis of these failed campaigns.
The West's declaratory strategy in Afghanistan was the fashionable notion of counter-insurgency warfare - COIN in the military vernacular. COIN was by no means a new concept, but its proponents asserted that a ''modern application'' would be ideally suited to Afghanistan.
In fact, this latest iteration turned out to be nothing more than a case of the emperor's new clothes - of a theory lacking intellectual credibility and, worse still, commonsense.
General David Petraeus was the US commander in Afghanistan during a critical phase of the invasion. Described as an expert in COIN, Petraeus at the time enjoyed enormous popular and political support, even though he was representative of a generation of Western army officers whose experience in the field was one of repeated failure.
The irony continues. Petraeus was also a principal author of the American Army's manual of counter-insurgency warfare, a booklet that had acquired near-mythic status among insiders. But according to Vietnam veteran, now academic, Andrew Bacevich, the manual was so vague and self-serving as to be meaningless. Bacevich's analysis was validated by the confusion that has characterised US military operations in Afghanistan.
Allegedly agile and flexible, in practice, Petraeus' so-called ''modern application'' of counter-insurgency warfare was reliant on the 19th-century dogma of mass, occupation, and seizing and holding ground. Not so much a strategy as a cult, it related to a world order that no longer exists.
If Australia is to salvage anything from the wreckage of Afghanistan, a vigorous public review of defence strategy must be conducted. That review would profit from the application of Obama's justified scepticism towards the process by which Western strategy is developed and advocated.
Dr Alan Stephens is a Canberra-based historian and a former RAAF pilot.