In a letter written in 1648, Swedish statesman Axel Oxenstierna, chancellor to both King Gustavus Adolphus and Queen Christina, counseled, "Know, my son, with how little wisdom the world is governed."

    The fighting between Russia and the former Soviet republic of Georgia is an unnerving reminder of that, and of how quickly the balance of global power can be tilted from unexpected directions with barely a warning.

    Some hawks and neo-cons called for NATO intervention or even suggested we send in Stinger missiles or the 82nd Airborne as a peacekeeping force. President Bush warned, "Russia has invaded a sovereign neighboring state and threatens a democratic government elected by its people. Such an action is unacceptable in the 21st century."

    Perhaps, but the reality of the early 21st century is that, in the short run, at least, the president's words ring hollow. In spite of past promises of support to Georgia, Russia is key to our efforts in the Middle East and our European allies are dependent on Russia for energy. The invasions of Afghanistan and Iraq have both our military strength and our international credibility stretched perilously thin at a time when oil-rich Russia is reemerging as a superpower. We've boxed ourselves in.

    It was in that light that I came upon the Oxenstierna quote the other night, while re-reading the late historian Barbara Tuchman's "The March of Folly," a knowing compendium, from ancient Troy to Vietnam, of the ways in which, given half a chance, those in power will steer their ships of state straight into the rocks. In the first chapter, she also quotes American President John Adams: "While all other sciences have advanced" - you can almost hear him sighing - "government is at a stand; little better practiced now than three or four thousand years ago."

    Andrew J. Bacevich probably would agree with all of the above. The retired Army colonel, a West Point graduate, teaches history and international relations at Boston University. His latest book, "The Limits of Power: The End of American Exceptionalism," explores our nation's current predicament, not just on the world stage, but here at home as well. He spoke with my colleague, Bill Moyers, on this week's edition of the PBS series, Bill Moyers Journal.

    Bacevich speaks truth to power, no matter who's in power, which may be why those of both the left and right are eager to hear his views. Perhaps it's also because when he challenges American myths and illusions, he does so from a genuine patriotism forged in the fire of his experiences as a soldier in Vietnam and the death a year ago of his son, an Army lieutenant in Iraq. "The Limits of Power" is dedicated to the young man, but the senior Bacevich, a man of quiet, solid gravitas, holds his grief privately between himself and his family.

    "Our foreign policy is something that is concocted in Washington, DC, but it reflects the perceptions of our political elite about what we the people want," he told Moyers. "And what we want, by and large is ... this continuing flow of very cheap consumer goods. We want to be able to pump gas into our cars regardless of how big they may happen to be. And we want to be able to do these things without having to think about whether or not the books are balanced at the end of the month, or the end of the fiscal year."

    To that end, he says, "One of the ways we avoid confronting our refusal to balance the books is to rely increasingly on the projection of American military power around the world to try to maintain this dysfunctional system or set of arrangements that have evolved over the last 30 or 40 years."

    "... I think historians a hundred years from now will puzzle over how it could be that the United States of America, the most powerful nation in the world, as far back as the early 1970's came to recognize that dependence on foreign oil was a problem, posed a threat, compromised our freedom of action. How every president from Richard Nixon down ... declared, 'We're going to fix the problem.' [But] none of them did."

    He continued, "The clearest statement of what I value is found in the Preamble to the Constitution. There is nothing in the Preamble to the Constitution which defines the purpose of the United States of America as remaking the world in our image, which I view as a fool's errand. I believe that the framers of the Constitution were primarily concerned with focusing on the way we live here, the way we order our affairs. To try to ensure that as individuals, we can have an opportunity to pursue our, perhaps, differing definitions of freedom, but also so that, as a community, we could live together in some kind of harmony. And that future generations would also be able to share in those same opportunities.... With the current crisis in American foreign policy, unless we do change our ways, the likelihood that our children, our grandchildren, the next generation will enjoy the opportunities that we've had is very slight because we're squandering our power. We are squandering our wealth."

    Bacevich believes, "The Congress, especially with regard to matters related to national security policy, has thrust power and authority to the executive branch. We have created an imperial presidency. The Congress no longer is able to articulate a vision of what is the common good. The Congress exists primarily to ensure the reelection of members of Congress."

    That imperial presidency, he says, "has made our democracy a false one. We're going through the motions of a democratic political system. But the fabric of democracy, I think, really has worn very thin."

    Iraq, Bacevich concludes, "was a fundamental mistake. It never should have been undertaken. And we're never going to do this kind of thing again." This might, he thinks, "be the moment when we look ourselves in the mirror [and] ... see what we have become. And perhaps undertake an effort to make those changes in the American way of life that will enable us to preserve for future generations that which we value most about the American way of life."

    Andrew Bacevich's words should echo down the corridors of Congress and the halls of the White House, no matter who becomes our next president.

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    The full broadcast of Bill Moyers Journal will be devoted to Bill's conversation with Bacevich (check local listings), and further discussion will continue online at the Moyers Blog.

    Michael Winship is senior writer of the weekly public affairs program, Bill Moyers Journal, which airs Friday nights on PBS. Check local airtimes or comment at The Moyers Blog at www.pbs.org/moyers.