Once upon a time, there was a grand and influential foreign policy doctrine. It was based on some traditional notions about U.S. statecraft that placed severe constraints on when America went to war. It asserted that when the United States used military force, it must do so in overwhelming fashion and only in the service of vital national interests. For any military action, it counseled the dispassionate weighing of costs and benefits, recommended that policymakers have clear, realistic and achievable political objectives, and called for the strong support of the American people and a clearly defined exit strategy.

This doctrine was called the Powell Doctrine, and it was based, in large measure, on a long-simmering debate in the military about how, when and where the United States should use force. While many in the military thought it was great, a lot of other folks hated it.

Liberal hawks were none too pleased because it precluded humanitarian interventions. During the Clinton administration, when then-Chairman of the Joint Chiefs of Staff Gen. Colin Powell (for whom the doctrine was named) argued forcefully against military adventurism to stop the bloodletting in the Balkans, Secretary of State Madeleine Albright demanded, "What's the point of having this superb military that you're always talking about if we can't use it?"

For neoconservatives, the Powell Doctrine was anathema because it precluded the sort of wars of choice and the muscular military strategy that they favored. Adherence to the Powell Doctrine made the notion of transformative military conflict virtually impossible.

In the 1990s, the liberal interventionists worked to soften the Doctrine's hard edges. While they abided by the notion that the United States must avoid long, drawn-out conflicts, they advocated utilizing force without clear political objectives, with only fleeting public support, and under a dubious interpretation of the national interest.

In the post-9/11 strategic environment, the Powell Doctrine was cast aside entirely. The subsequent invasion of Iraq violated virtually every one of its tenets. That its namesake, Colin Powell, was serving as U.S. Secretary of State at the time is perhaps the Doctrine's greatest and most disturbing irony.

More than a quarter-century after it first entered the strategic consciousness of the U.S. national security bureaucracy, we don't hear much about the Powell Doctrine anymore. It has seemingly become a precious artifact of a bygone era in U.S. statecraft.

Yet, the lack of attention today to the key attributes of the Powell Doctrine is difficult to understand. After the twin conflicts of Iraq and Afghanistan, the more than 5,000 American troops killed, the hundreds of billions -- even trillions -- of dollars spent, it's hard to imagine a strategic doctrine that is more appropriate.

Unfortunately, the lesson seemingly being drawn from these two wars is not that the U.S. must avoid the sort of draining, manpower-intensive and time-consuming counterinsurgency operations that have defined the U.S. missions in Iraq and Afghanistan. Instead, the moral of Iraq and Afghanistan seems to be that the United States must learn to fight these types of conflicts more effectively, because they are the future of war.

Meanwhile, the lessons of the Powell Doctrine and a restrained notion of when military force should be exercised are gathering cobwebs in the U.S. strategic toolbox. The time has come, however, to dust off this old war horse, because it is perhaps more relevant and timely than ever.

The Legacy of Vietnam

The Powell Doctrine emerged out of the Vietnam War, and specifically the belief by many in the military that U.S. troops should never again be asked to fight a similar type of conflict. Its antecedents can be found in the "Never Again vs. Limited War" debates of the 1950s and 1960s, following America's experience in the Korean War. The Never Again side argued that the U.S. should either do everything necessary to win future wars or not fight them at all -- that is, total war or none at all. The Limited War advocates argued that the U.S. could expect a future of limited regional wars, like Korea, so it was best to be prepared for them. The Vietnam War, while offering support to the Limited War advocates' analysis on a tactical level, ultimately made the strategic argument of the Never Again camp even more resonant.

A decade later, the ill-fated U.S. intervention in Lebanon in 1983 exemplified the pitfalls of an open-ended approach to the use of military force. Sent to perform "peacekeeping" duties in the midst of a five-sided ethnic conflict, the U.S. quickly found itself taking sides. Soon after, 241 Marines would be killed when a suicide bomber attacked their barracks.

The Lebanon debacle led then-Secretary of Defense Casper Weinberger to update the Never Again argument in a speech to the National Press Club in Washington, where he offered a new and more restrained construct for the future use of American military force. Weinberger laid out six clear criteria that he believed should guide policymakers' decision-making:

1) The United States should not commit forces to combat overseas unless the particular engagement or occasion is deemed vital to our national interest or that of our allies.
2) If we decide it is necessary to put combat troops into a given situation, we should do so wholeheartedly, and with the clear intention of winning.
3) If we do decide to commit forces to combat overseas, we should have clearly defined political and military objectives.
4) The relationship between our objectives and the forces we have committed -- their size, composition and disposition -- must be continually reassessed and adjusted if necessary.
5) Before the U.S. commits combat forces abroad, there must be some reasonable assurance we will have the support of the American people and their elected representatives in Congress.
6) The commitment of U.S. forces to combat should be a last resort.

Weinberger's doctrine, which had strong support among the uniformed military, was fleshed otu further by Colin Powell in 1992. But the bottom line remained unchanged: The criteria for the use of force must be stringent, and the full consequence of what military action would entail must be carefully considered.

Embrace and Then Pushback

The test case for the Powell Doctrine would be the First Gulf War of 1990-1991, which embraced several of its key attributes: domestic and overseas support -- military action was endorsed by a U.N. mandate; clear political and military objectives -- removal of Saddam Hussein from Kuwait; the use of force as a last resort -- diplomatic negotiations continued until the last minute; and a level of force committed to battle that was more than commensurate to the goals that the United States was seeking to achieve. Perhaps most questionable was the notion that the liberation of Kuwait fell within America's national interests. But it was hard to argue with the success of a military endeavor that achieved its immediate goals and was completed within 100 hours.

Over the next dozen years, leading policymakers would nibble away at the constraints put in place by the Doctrine. In Somalia, for instance, the military mission was initially dedicated to providing humanitarian relief for starving refugees. But it eventually evolved into a nation-building exercise, in which the military became directly involved in the internal politics of what was, by all accounts, a non-functioning state. The result was depressingly similar to the carnage in Lebanon. Nineteen dead U.S. soldiers and the televised images of their bodies being dragged through the streets of Mogadishu quickly ended the U.S. misadventure in the Horn of Africa.

In the Balkans, liberal hawks would again push for the use of force. But fear of a repeat of Mogadishu and the uncertainty about what military intervention could hope to achieve in the midst of a multi-ethnic civil war stifled the calls. Even so, in March 1996, National Security Adviser Tony Lake laid out an updated version of the Powell Doctrine that advocated the selective but substantial use of force in support of diplomatic or political objectives. Lake was careful, though, to formalize a new constraint: "Before we send our troops into a foreign country, we should know how and when we're going to get them out."

Under the umbrella leadership of NATO, such a selective use of force was utilized in Kosovo. Once again, the fear of involving U.S. forces in a long, drawn-out conflict limited the role played by ground troops. But what was perhaps most significant about the Clinton years was the increasingly elastic definition of America's national interests. While Weinberger and Powell had advocated the use of force only in defense of U.S. vital national interests, the 90s saw force being used in places where the direct impact on America's national interests was more difficult to decipher.

Perhaps some loosening of the Powell Doctrine's constraints was in order. As long as policymakers were cognizant of the risks, the selective application of force could bring positive results -- as was seen, to a limited extent, in the Balkans, and against Iraq in 1998. But it was a slippery slope, and as time would soon tell, one that could easily be exploited at a time of national trauma.

The Post 9/11 Environment

In the aftermath of 9/11, the restraints imposed by the Powell Doctrine were summarily cast aside. Emboldened by a surrounding cadre of neo-conservatives, for whom the use of U.S. military force was a vital tool of national statecraft, President George W. Bush quickly became a proponent of military intervention and nation building, despite having warned about the perils of such endeavors as a candidate. In Afghanistan, Bush pledged to "continue helping [Afghans] secure their country, rebuild their society and educate all their children, boys and girls." Only weeks after this almost-casual declaration, the U.S. would invade and occupy another Muslim country.

The strategic planning behind the invasion and occupation of Iraq represented the antithesis of the Powell Doctrine. In the spring of 2003, there was no clear political objective to the war in Iraq, only the tactical objective of removing Saddam Hussein from power. Non-violent measures or even alternative force packages were not considered. Indeed, even non-military measures that had begun to show effectiveness -- for instance, U.N. inspectors that the Iraqi regime reluctantly allowed back into the country -- were ignored or disregarded. Virtually no thought was given to the long-term consequences of invading and occupying Iraq. According to the Army's official history of the war, "There was no adequate operational plan for stability operations and support operations." The war barely had majority public support in the U.S., and by its later stages was deeply unpopular, while key allies were opposed to it from the outset. Finally, there was no exit strategy in place for the departure of U.S. troops.

That the war in Iraq bore striking similarities to the debacle in Vietnam was hardly a coincidence. Like Vietnam, the Iraq war was fought on a foundation of shaky political and military assumptions that failed to adequately consider the full consequences of going to war. As Clausewitz might have suggested, "No one starts a war -- or rather, no one in his senses ought to do so -- without first being clear in his mind what he intends to achieve by that war, and how he intends to conduct it." But that is precisely what the United States did in Iraq.

On a deeper level, what these two wars have in common with each other -- and with Lebanon, Somalia and even Afghanistan -- is that, as Michael J. Mazarr suggests, "such conflicts will inevitably be strictly limited for the United States, whereas for its enemies, they will often approach absolute warfare." Rarely considered in all these conflicts, was the political will, devotion and even fanaticism of potential rivals, as well as their patience for armed conflict. Perhaps the most important, yet unstated element of the Powell Doctrine was the understanding that open-ended conflicts defined by anti-guerrilla and counterinsurgent operations were rarely in the U.S. national interest, because the political will to see such conflicts to the end was in short supply on the U.S. side -- and in great supply among its enemies.

Lessons Unlearned

One might imagine that after Iraq -- a military and political debacle on a par with Vietnam -- the military and civilian leadership would be running with open arms to embrace a doctrine that keeps them out of protracted conflicts with undefined political objectives that do not serve the national interest.

Yet, the exact opposite is occurring. If there are any lessons to be learned from the first four years of the Iraq War, they are that force must be a last resort, that the United States is ill-equipped to do effective and long-term nation-building, that military incursions must be limited and that they must be combined with a clear and realistic political objective. But instead, many in the military and civilian leadership are focusing on the transitory success of the past two years in Iraq. They argue that the counterinsurgency techniques used there not only stabilized the situation in Iraq, but are applicable to future conflicts like the ongoing war in Afghanistan.

Even setting aside the fact that the claims of success for counterinsurgency tactics in Iraq are incomplete and premature at best, it is inexplicable that debate is so rare over whether a robust counterinsurgency effort in Afghanistan is worth the necessary blood and treasure, and whether it serves the national interest.

Consider the words of a key advocate of counterinsurgency, John Nagl, president of CNAS and co-author of the Army and Marines counterinsurgency manual, FM 3-24:

After Vietnam, the phrase "never again" meant many things to many people, but generally indicated the Army should never again fight a protracted war without the support of the American people. Today, we should continue to vow "never again" -- but this time, that we never again focus so exclusively on preparations to decisively defeat any enemy on the conventional battlefield that we neglect to achieve the same degree of proficiency in winning the peace that follows. Sept. 11 conclusively demonstrated that instability anywhere can be a real threat to the American people here at home. Defeating instability through effective counterinsurgency operations is therefore a core mission of the Defense Department. We must take counterinsurgency as seriously as we take ensuring success in major combat operations.

It is difficult to accept the notion that counterinsurgency is or should be a core mission of the military. But perhaps an even more important question for policymakers to ask is whether the U.S. should be fighting counterinsurgencies at all.

Instead, criticism of the U.S. decision to go to war in Iraq in the first place has been replaced with an altogether different critique: that the U.S. military forgot the lessons of counterinsurgency learned in Vietnam and earlier conflicts. As a result, the military was ill-prepared for the counterinsurgent and pacification campaigns it faced in Iraq.

While this is a legitimate critique, it misses the bigger picture. Instead of addressing the strategic flaws that underpinned the pre-war planning for Iraq, many students of the Iraq war are instead confining their examination to a question of tactics. But the central problem with the Iraq War is not how the United States chose to fight it. Rather, it's that the United States chose to fight it at all.

As the CATO Institute notes "What Iraq demonstrates is a need for a new national security strategy, not better tactics and tools to serve the current one. By insisting that there was a right way to remake Iraq, we ignore the limits on our power that the enterprise has exposed and we risk repeating our mistake."

Who Gets the Vote

Some advocates for counterinsurgency suggest that the so-called Long War against jihadist terrorists will necessitate more, not less, intervention. These arguments often minimize the very agency of the United States in determining when and how it goes to war. According to Max Boot, "Unfortunately, the United States cannot determine the nature of its future wars; the enemy has a vote, and the more evident the U.S. inability to deal with guerrilla or terrorist tactics, the more prevalent those tactics will become."

But guerrilla tactics are generally utilized against U.S. forces only after a U.S. military intervention has occurred. As Andrew Bacevich perceptively argues, "If counterinsurgency is useful chiefly for digging ourselves out of holes we shouldn't be in, then why not simply avoid the holes? Why play al-Qaida's game? Why persist in waging the Long War when that war makes no sense?"

Boot goes even further, though, arguing that "defeating terrorism, as Washington has learned in Afghanistan, requires putting boots on the ground and engaging in nation building." By this argument, the only appropriate response to terrorist provocation is to slug it out in foreign lands and "remake entire societies," a course of action that plays directly into the hands of America's enemies. There is, according to Boot, virtually no middle course.

But while America's enemies might get a vote on the nature of future wars, the United States has a veto on whether or not to engage in them. Those who would argue that the United States must continue to chase terrorists around the globe with fulsome military interventions, as opposed to seeking a policy of containment, might want to consider the trillions already spent in Iraq and Afghanistan, not to mention the deaths of more than 5,000 American soldiers, in pursuit of just such a strategy.

Restoring the Advisory Role in Civil-Military Relations

Many of the counterinsurgency advocates have argued that the type of counterinsurgency operations necessary for fighting the Long War are difficult, but that the military must be prepared for them if the President requests such an operation. But this can easily become a self-perpetuating argument.

It's worth remembering that the architects of the Powell Doctrine came out of the military. They pushed civilian policymakers to see the benefits of placing more stringent constraints on the use of military force. The military's job is, of course, to carry out the orders of the commander-in-chief, but this does not mean the armed forces can simply cast aside their advisory role to the civilian leadership.

Rather than devoting so much energy to preparing the military to fight counterinsurgency, such advocates should be patiently explaining all the many reasons why we should avoid them at all costs. Instead, they are orienting army doctrine and key resources toward counterinsurgency, and making it the guiding logic of America's mission in Afghanistan. The danger is that they convince policymakers, whether intentionally or not, that we're so good at these types of operations, we should be doing more rather than less of them.

If the experiences of the past eight years have taught us anything, it is that the bar for overseas intervention should be returned to the level suggested by Powell and Weinberger. The Iraq War, in particular, is an object lesson in the limits and efficacy of American power, and the ineffectiveness of military force in fighting non-state actors, such as terrorists.

Some have argued that since you can't predict the future of war, the U.S. must be prepared for the full spectrum of possible conflicts. But while the future may be unknowable, the criteria by which we use force need not be. The United States must prepare for the conflicts that are not only in the country's vital interests, but that it can also bring to a satisfactory conclusion. That's the essence of the Powell Doctrine, and why it deserves reconsideration. To be sure, this doesn't mean a slavish devotion to the criteria outlined by either Weinberger or Powell. There will always be times when the limited use of force is appropriate. But it does mean a far more rigorous consideration of costs and benefits, as well as the national interest, before such force is employed.

If recent history teaches us anything, it is that the use of American military force can and usually does engender its own set of unintended and unexpected consequences. The fact that America's fighting men and women continue to die in Iraq and Afghanistan nearly eight years after the attacks of Sept. 11 is perhaps the most compelling and tragic reminder of that fact.

In the haunting movie, Fog of War, former Secretary of Defense Robert McNamara spoke eloquently about the basic, unknowable element of human conflict. "War is so complex, it's beyond the ability of the human mind to comprehend all the variables. Our judgment, our understanding, are not adequate. And we kill people unnecessarily." It's a lesson worth remembering as the United States begins to think about a post-Iraq and even a post-Afghanistan future.