The rare resignation on principle is always telling in American government. When Matthew Hoh recently left the State Department -- a Marine Captain in Iraq who became a diplomat in Afghanistan -- his act was significant far beyond the first reports.

Hoh speaks grim truth to power. His message is that to pursue the Afghan war policy in any guise -- regardless of the troop level President Obama now chooses -- will be utter folly, trapping America in an unwinnable civil war in the Hindu Kush, and only fueling terrorism.

An advisor in southern Afghanistan, Hoh knew the malignancy of want behind the war. Eight years after the U.S. invasion and a third of a trillion dollars spent, half the nation faces starvation on 45 cents a day, half the children die before five, and half the surviving young have no schools, part of a torment Afghans plead in poll after poll to be understood as the core of their conflict. He knew well the source of that scourge in the U.S.-installed Kabul regime, a kleptocracy of war- and drug-lords holed up amid American bodyguards in "poppy palaces," while clan-based "security forces" loot the countryside, sodomize its sons, and swell insurgent ranks. "We're propping up a government," Hoh said last week, "that isn't worth dying for." So pervasive and profound is that corruption, so entwined with the private exploitation and official graft of the U.S. occupation regime -- including kickbacks or extortion payments from both the American military and civilian aid programs to both the new Kabul plutocracy and the multi-layered Taliban -- that the morass makes every other issue of policy moot.

The 36-year-old diplomat brings unique authority to public debate. An insider confirming outside critics dispels the myth that classified information redeems a failed policy. He also speaks to and for many in government, infusing honesty where folly feeds on wary quiet and fraudulent unanimity. "There are a lot of guys, not just in the Foreign Service but in the military, who are looking at this thing and they don't understand what we are doing there," he told one audience. "I get mails all the time from junior and mid-level officers telling me, 'Keep it up. This makes no sense to us.'"

Whatever this protest says outwardly, its deeper meaning is devastating. The sheer contrast between Hoh and senior officials -- seeing the same reality, the same reports -- exposes some dirty little secrets of policy haunting the Obama presidency.

With the 8-year enormity of waste, venality and oppression since the invasion of 2001, ravages Hoh saw climaxed around him, went the knowing silence if not collusion of a succession of U.S. diplomats and officers responsible in the defiled occupation of Afghanistan. There is a troubling legacy, too, in the policy process. In the grip of experience irrelevant in Afghanistan, a generation of military commanders comes with a crudely recycled but promotion-rich creed of counter-insurgency, avenging what some as young officers in the 1970s saw as a false defeat if not home-front betrayal in Vietnam. They are allied with the lucrative in-and-out careerism of powerful if publicly faceless civilian Pentagon officials, what State Department rivals call the "COIN-heads" of counter-insurgency dogma. Those currents run like a murky subterranean river beneath the doomed policy Hoh silhouettes.

Most telling may be the disparity between Hoh -- the serious student of Afghan culture -- and Washington's decision-makers. To deal with one of the most complex settings on earth, the Obama administration relies on key figures -- Secretary of State Hillary Clinton, Defense Secretary Robert Gates, Af-Pak Special envoy Richard Holbrooke and NSC Advisor James Jones -- whose careers in politics or the bureaucracy (like those commanding generals David Petraeus and Stanley McChrystal) are bereft of any substantive knowledge of a people they are supposed to master. It leaves them all dangerously dependent on staff, and prey to the absence of dissenters like Hoh among aides whose credentials are hardly more impressive than their own.

That intellectual vacuum, a mirror of Vietnam decision-making, explains the shock and hostility that greeted recent cables of US Ambassador Karl Eikenberry opposing added U.S. troops backing an irredeemable regime. As Hoh exemplifies, actual knowledge of Afghanistan is rare -- and the lack scarcely recognized -- in a war council prone to flippant lines like Clinton's recent "There are warlords and there are warlords," or Holbrooke's definition of success, "We'll know it when we see it."

At the heart of Washington's decision-making dysfunction, of course, is always a president in thrall to the hoary fears and myths of national security, the most important realm he governs and in which most take power least prepared. For Barack Obama, only historic courage and insight can surmount the multiple corruptions of policy he is heir to.

Hoh embodies that bravery. Implored by Eikenberry to stay, he chose to forgo a prized career to speak out. We know that agony. There is no easy course ahead in Afghanistan. US policies a half century before 2001 account for much of the politics now so deplored in Kabul, a breakdown inflicted as well as inherent, and a blood debt added to the toll of occupation and war.

The gruesome truth of that history is that our sacrifices so far have been largely in vain. It is Matthew Hoh's heroism to try to stop the inseparable casualties of lives and truth.