On October 1, 1950, the forces of a U.S.-led coalition, acting under the authority of a UN resolution, drove the forces of the Korean People’s Army across the 38th parallel and back into North Korea. It was the culmination of a string of stunning military victories.

From the surprise North Korean invasion in June, U.S.-led forces had taken just four months to mount an amphibious landing at Inchon, break out from defensive lines around Pusan and drive the KPA into headlong retreat.

With the North Korean forces routed, the United States was in a position to dictate the terms of peace. Instead (with Russia absent) the United States secured a UN resolution demanding the reunification of Korea. By October 19, U.S. forces had occupied Pyongyang (the first and almost certainly the only time the United States captured a communist capital). Not satisfied with this, General Douglas Macarthur pushed on rapidly. By the end of October, his forces were close to the Yalu River, marking the border with China.

Although China had repeatedly threatened to intervene in the war, the first Chinese attack on U.S. forces took Macarthur completely by surprise. The result was a bloody and humiliating retreat, ending in the loss, for the second time, of Seoul. Three years and millions of deaths later, the active phase of the war ended with the restoration of the territorial status quo ante.

This disaster is of more than historical interest. As David Halberstam pointed out in The Coldest Winter, Macarthur’s staff “doctored the intelligence in order to permit MacArthur's forces to go where they wanted to go militarily. . . . In the process they were setting the most dangerous of precedents” for the misuse of intelligence to justify the Vietnam and Iraq wars.

Equally important is the pattern of overreach, by which the United States has repeatedly turned initial military success into costly defeats or quagmires. The most obvious examples are the current wars in Iraq and Afghanistan, but the interventions in Lebanon and Somalia also fit the pattern. In Lebanon, a U.S.-led Multinational Force (MNF) was initially authorized to oversee PLO withdrawal from Beirut, a task accomplished within a couple of weeks. Following the Sabra and Shatila massacres, however, the MNF was sent in again, this time without a clearly defined goal. The mission ended in disaster when the MNF barracks was hit by a truck bomb, killing over two hundred U.S. and French troops. In Somalia, what was initially a successful famine-relief mission (Operation Restore Hope) was converted to a nation-building exercise (Operation Continue Hope). It was abandoned after the “Black Hawk Down” incident in Mogadishu. Leaving aside the absence of an initial victory, Vietnam fits the pattern as well.

The Powell doctrine, developed in the lead-up to the First Gulf War, was designed to ensure that America avoided this kind of failure. Powell stressed the importance of limited, well-defined objectives and a clear exit strategy. This was influential to the extent that President George H. W. Bush did not send U.S. troops to Baghdad. But since then, the problem of overreach has been more the rule than the exception.

In 2002, the U.S. administration achieved its stated goals without firing a shot when Saddam Hussein readmitted UN weapons inspectors and allowed them free access to suspected sites—where, of course, they discovered nothing. By the time of the invasion, they had advised that the completion of their task would take “not years, not weeks, but months.” Nevertheless, the invasion went ahead under the assumption that most U.S. forces would be withdrawn by 2005 at the latest, with Bush administration officials estimating a total cost of $50–60 billion.

What accounts for this pattern? In part, it reflects the maxim, “To a man who has only a hammer, every problem looks like a nail.” The U.S. military has the capacity to defeat any conventional military force that might oppose it, with remarkable ease. The idea of such easy victories leads to assumptions that the military must be ideally suited to any task assigned to it, from overseas nation building to domestic disaster relief.

Thus, the very invincibility of the military creates its own problems. With the exception of the deluded Saddam Hussein, no opposing army has been willing to take on the United States in a conventional war since Korea. As a result, proposed military actions almost never satisfy the stringent requirements of the Powell doctrine. As Madeleine Albright famously put it, "What are you saving this superb military for, Colin, if we can't use it?” This concept gives U.S. policy makers a strong incentive to find uses for their resources.

Another contributing factor, paradoxically, is that Americans, like most citizens of prosperous and democratic countries, are generally not enthusiastic about war as a policy. The use of military force needs a strong justification to overcome this instinctive opposition, and this typically means statements of lofty goals. When it turns out that these goals are unachievable, they can’t be abandoned without an admission that the original decision to go to war was based on mistaken premises. So ending a failed war typically requires the departure of the administration that started it.

Even then, an explicit admission of failure is unacceptable in a democratic system. Thus did Obama’s withdrawal from Iraq have to be accompanied by praise for the "extraordinary achievement" of a venture which trillions of dollars and thousands of American lives, for what turned out to be little benefit to the United States and catastrophic for millions of Iraqis.

Can anything be done to break out of this pattern of overreach? At present, the signs are not hopeful. Support for large-scale armed intervention has ebbed somewhat, but it has been replaced by an equally naive enthusiasm for drone warfare directed at an ever-expanding list of enemies (along with unfortunate bystanders and victims of mistaken identity). The realization that military power is a vital tool but one with a very limited range of effective uses will be a long time coming.

John Quiggin is a professor of economics at the University of Queensland, Australia, and adjunct professor at the University of Maryland, College Park. He is author of Zombie Economics: How Dead Ideas Still Walk Among Us (Princeton University Press, 2010).