For the second time in a generation, the United States faces the prospect of defeat at the hands of an insurgency. In April 1975, the U.S. fled the Republic of Vietnam, abandoning our allies to the North Vietnamese communists. In 2007, Iraq's grave and deteriorating condition offers diminishing hope for an American victory and portends risk of an even wider and more destructive regional war.

These debacles are not attributable to individual failures, but rather to a crisis in an entire institution: America's general officer corps. America's generals have failed to prepare our armed forces for war and advise civilian authorities on the application of force to achieve policy aims.

Following World War II, there were ample indicators that America's enemies would turn to insurgency to negate our advantages in firepower and mobility. In 1961, President Kennedy warned of "another type of war, new in its intensity, ancient in its origin — war by guerrillas, subversives, insurgents, assassins, war by ambush instead of by combat, by infiltration instead of aggression, seeking victory by evading and exhausting the enemy instead of engaging him."

Despite the experience of their allies and the urging of their president, America's generals failed to prepare their forces for counterinsurgency. America's generals also remained largely silent while the strategy developed by civilian politicians led to defeat. President Johnson made a concerted effort to conceal the costs and consequences of Vietnam from the public, but such duplicity required the passive consent of America's generals.

Now, America's generals have repeated the mistakes of Vietnam in Iraq.

For reasons that are not yet clear, America's general officer corps underestimated the strength of the enemy, overestimated the capabilities of Iraq's government and security forces and failed to provide Congress with an accurate assessment of security conditions in Iraq. Moreover, America's generals have not explained clearly the larger strategic risks.

The most fundamental military miscalculation in Iraq has been the failure to commit sufficient forces to provide security to Iraq's population.

Given the lack of troop strength, not even the most brilliant general could have devised the ways necessary to stabilize post-Saddam Iraq. However, inept planning for postwar Iraq took the crisis caused by a lack of troops and quickly transformed it into a debacle. The military never explained to the president the magnitude of the challenges inherent in stabilizing postwar Iraq.

After failing to visualize the conditions of combat in Iraq, America's generals failed to adapt to the demands of counterinsurgency, treating efforts to create transition teams to develop local security forces and provincial reconstruction teams to improve essential services as afterthoughts.

The intellectual and moral failures common to America's general officer corps in Vietnam and Iraq constitute a crisis in American generalship. Any explanation that fixes culpability on individuals is insufficient. No one leader, civilian or military, caused failure in Vietnam or Iraq. Different military and civilian leaders in the two conflicts produced similar results. In both conflicts, the general officer corps designed to advise policymakers, prepare forces and conduct operations failed to perform its intended functions.

Neither the executive branch nor the services are likely to remedy the shortcomings in America's general officer corps. Indeed, the tendency of the executive branch to seek out mild-mannered team players to serve as senior generals is part of the problem. The services themselves are equally to blame. In a system in which senior officers select for promotion those like themselves, there are powerful incentives for conformity.

To improve the creative intelligence of our generals, Congress must change the officer promotion system in ways that reward adaptation and intellectual achievement. The Senate would never confirm to the Supreme Court a nominee who had neither been to law school nor written legal opinions. However, it routinely confirms four-star generals who possess neither graduate education in the social sciences or humanities nor the capability to speak a foreign language.

To reward moral courage in our general officers, Congress must ask hard questions about the means and ways for war as part of its oversight responsibility. Congress must ask for a candid assessment of the money and manpower required over the next generation to prevail in the Long War, and demand that procurement priorities reflect the most likely threats. Current oversight efforts have proved inadequate, allowing the executive branch, the services and lobbyists to present information that is sometimes incomplete, inaccurate or self-serving.

America's generals spent the years following the 1991 Gulf War mastering a system of war without thinking deeply about the ever-changing nature of war. They marched into Iraq having assumed without much reflection that the wars of the future would look much like the wars of the past. Those few who saw clearly our vulnerability to insurgent tactics said and did little to prepare for these dangers.

The hour is late, but not too late to prepare for the challenges of the Long War. We still have time to select as generals those who possess the intelligence to visualize future conflicts and the moral courage to advise civilian policymakers on the preparations needed for our security.

Army Lt. Col. Paul Yingling is deputy commander, 3rd Armored Calvary Regiment. He served two tours in Iraq, another in Bosnia and a fourth in Operation Desert Storm. The views expressed here are the author's and do not necessarily reflect those of the Army or the Defense Department.