Years from now, when today's lieutenants and ensigns are generals and admirals, what will make them nervous? That is, what will be the "Vietnam syndrome" equivalent applied to those in uniform today, battlefield experiences they had that raise warning flags when they're asked to fight again?
That will be one very pointed way of considering whether the lessons of US operations in Iraq have been learned. With the symbolic handover of Iraq to Iraqis this week, that examination of US military doctrine and tactics there officially begins.
But like Vietnam and World War II, such lessons aren't confined to Pentagon planners and service academy professors. They are inevitably connected to how political leaders and Americans generally - those who send service men and women into harm's way - see the role of the United States in the world.
Among the questions raised by a war that has been longer and costlier than anticipated: What kind of future conflicts should be expected and prepared for? How will the makeup and placement of US forces around the world change? And perhaps most important to those who do the nation's fighting: What's the outlook for shoot-first "preventive war" as advocated by neoconservatives prominently advising the president?
Much of the discussion revolves around the so-called Powell Doctrine of war (explicit objectives, overwhelming use of force, clear exit strategy) versus the "Rumsfeld Doctrine" (smaller numbers of highly maneuverable ground forces, emphasis on special operations, and high-tech air power).
At this point, there are more questions than answers. But a few things are certain.
"Marines and Army will resemble each other more and more - light, mobile, transportable," says retired Army Col. Daniel Smith, military affairs analyst at the Friends Committee on National Legislation in Washington. "Heavy armor will be downplayed. Heavy artillery will be downsized. Special operations units - SEALs, Air Force special ops, Green Berets, Delta [forces] will be larger and more active."
Of all the services, the Army is likely to see the greatest longer-term effects of the Iraq war, many experts predict, beginning with the clear need to prepare for messy political conflicts, insurgencies, and peacekeeping operations rather than focusing so much on conventional combat.
"The Army's most recent failure to accelerate transformation for these new types of operations can be somewhat understood given that the administration came in saying 'no nation-building,' " says military analyst Marcus Corbin of the Center for Defense Information in Washington. "Now that the administration has dumped on the Army the biggest nation-building in decades, no longer can the Army leadership hide behind that excuse."
In Iraq, "shock and awe" from the air allowed for US ground troops' quick dash to Baghdad. But it also sent most of Saddam Hussein's loyalist forces underground, thereby setting the scene for an insurgency that continues to seriously undermine efforts at reconstruction.
"The real lessons of Iraq are that the nature of conflict has changed and that our military doesn't perform very well in these new circumstances," saysretired Navy Capt. Larry Seaquist. For example, says Captain Seaquist, the so-called information revolution did not furnish critical intelligence information.
"The huge investment in computer networks, drone aircraft, and the other high-tech gadgetry failed to provide situational awareness about the only thing that counted - which Iraqis favored and which opposed the occupation," says Seaquist. "That failure led to the need to snatch thousands of Iraqis for interrogation - a strategy that turned out not only to be ineffective but a strategic disaster for the entire enterprise."
In response to shifting security needs, troop transfers worldwide will continue with an emphasis on smaller, more mobile units in strategically important places such as the Horn of Africa, the Indian Ocean, and Eastern Europe. Traditional large deployments in South Korea; Germany; and Okinawa, Japan, will be reduced. Most units will be home-based in the US, says Colonel Smith, rotated to small, forward-operating bases that also serve as training locales.
The US occupation of Iraq was ceremoniously declared to have ended this week, but American soldiers in large numbers are likely to be there for the equivalent of a full career.
"The surprise-free assumption would be 50,000 US troops in Iraq for at least the next generation, along with the current footprint in Central Asia for at least as long," says John Pike, of GlobalSecurity.org in Alexandria, Va.
One lesson of Iraq may be that nationalism and tribalism are so strong now that nation building is a process that should be avoided.
"Yes, the Pentagon botched the planning for the Iraq occupation," says national-security specialist Ivan Eland of the Independent Institute in Oakland, Calif. "But no amount of good planning could have surmounted the herculean task of remaking an entire society from the ground up, especially a fractious one like Iraq with no experience with democracy."
What the next generation of military leaders will have to wonder is: In an uncertain world with new threats, will their civilian leaders decide that such a herculean task is unavoidable?
"I do think there's a big story coming out of the huge volume of Army officers who will have rotated through Iraq and seen [future] needs," says Mr. Corbin at the Center for Defense Information. "That kind of near universal common experience in a bureaucracy creates a vital shared understanding and language that can be the base for broad institutional change."