The U.S. military has been engaged in constant combat in Southwest Asia for nine years, from the first deployment into Afghanistan only weeks after 9/11 to the surge there in August 2010, even as U.S. combat forces withdrew from Iraq.

It is the longest period of sustained combat since Vietnam – but the differences between the two conflicts and the structure of the U.S. military have far-reaching implications for the future.

Vietnam was fought largely by draftees, the vast majority of whom left the service at the end of their required term; all U.S. warfighters in Southwest Asia are volunteers in a professional military. And while Vietnam was the only conflict in U.S. history that did not involve extensive use of the National Guard and Reserves, those elements have provided roughly half the combat troops deployed to Iraq and Afghanistan.

While many veterans of World War II served two or more successive years in theater, in a war involving a far larger number of soldiers, sailors, airmen, and Marines, they, too, largely returned to civilian life as the postwar military was significantly downsized.

The Army estimates more than 55 percent of today’s active, Guard, and Reserve members have been deployed into combat at least once. The percentage for the Marine Corps is even higher, while the Navy and Air Force, with a far less active role in this conflict after the first two years, have lower rates, with the exception of certain specialties, such as special operations and medical.

The result is a corps of officers and non-commissioned officers (NCOs) – not only active duty, but Guard and Reserve as well – who will often carry extensive, multiple tour, combat experience into their future assignments, from training to combat, acquisitions and program management to senior leadership and planning. For at least the next decade, more than any other in U.S. history, the military – especially the Army and Marine Corps – will be led by battle-hardened, combat-experienced warfighters.

“For the first time, you have an all-volunteer force that has been able to sustain itself and bring back combat experience – and not just in terms of counterinsurgency [COIN],” said John Grady, spokesman for the Association of the U.S. Army (AUSA) and an Air Force Vietnam veteran. “As the Army withdraws from Southwest Asia, you will be able to put even more into their training beyond COIN and civil military affairs and into the full spectrum of operations in terms of major ground combat.”

“About the only combat experience [resident in the military] prior to this was Grenada, Panama, the first Gulf War, and Somalia, which was quite different from the first three. There may have been some special forces working with different countries involving insurgencies, such as the Philippines and in Central America. But aside from that, it was basically garrison duty and forward deployment in Korea and Europe. Even the Balkans, in the mid-1990s, was not combat but more like peace enforcement, keeping the parties separated to allow the establishment of some type of civil order under U.N. supervision.”

In addition to moving from the draft to an all-volunteer force – now considered the permanent model for U.S. force projection in the future – the Army also changed from sending individual replacements, as was done in most previous wars, to units replacing units.

“So you now have people moving into leadership roles who have experienced combat and understand the value of unit cohesion, partly as a result of the replacement policy. They also know they need to learn as much as possible in advance of any future operations,” Grady added. “One thing picked up early was not just a unit being deployed contacting the unit they are replacing to better understand the major players and what is happening, but also host nation district and local level officials with whom they would be working for the next year.

“There is a greater understanding about the need for interagency cooperation and how a military commander works with both U.S. and host country civil authorities. These are not just military operations, but have a major civil component, involving everyone from the State Department and Agriculture to the Drug Enforcement Agency, FBI, and CIA. For the first time in the U.S. military, you have an understanding, at both the officer and NCO level, that this is critically important to the success of any mission.”

Army Chief of Staff Gen. George W. Casey, Jr. has warned that the nation is facing an undetermined period of “persistent conflict,” even as the military struggles to deal with the cumulative effects of nine years of combat and how those will manifest themselves among both warfighters and their families.

“We’re building an Army that is a versatile mix of tailorable and networked organizations operating on a rotational cycle, to provide a sustained flow of trained and ready forces for full spectrum operations and to hedge against unexpected contingencies, at a tempo that is predictable and sustainable for our all-volunteer force,” Casey said. “That’s what we’re doing. That’s the direction we’re headed. I believe it will give us exactly the kind of Army we’ll need for the challenges of the 21st century.”

It is a future Casey and other military and civilian leaders believe will see a combination of terrorist attacks, such as 9/11 and the public transportation bombings in Spain and England, insurgencies that may cross national borders, diplomatic and civil tensions, and transnational movements not directly connected to any government, such as drug cartels and al Qaeda. Grady cites the Haqqani network in eastern Afghanistan and western Pakistan, which began as the mujahideen freedom fighters during the Soviet occupation of Afghanistan, but now have their own agenda, which may or may not include the Taliban.

“It’s hard to tell, but they are definitely a factor,” he said. “And you already see that being taken into account in the curriculum at the Army Command and General Staff College, as well as NCO training. Civil affairs also are now woven into exercises at the Fort Polk [La.] and Fort Irwin [Calif.] training centers and at Hohenfels in Germany, where they deal with scenarios that were not done before.”

From field training to war colleges to basic training, combat-experienced officers and NCOs are the training officers and drill instructors (DIs) sharing their battle experience with new enlistees and junior officers.

“Today’s DIs are volunteers who want to share what they know with those coming after them, try to give what they learned to the young men and women who will fill the ranks, talking soldiers through the issues they faced in combat and how they can become technically better at what they do,” Grady added.

“You see the same thing with officers, sharing with each other the difficulties they have experienced. There also is a very active Center for Army Lessons Learned at Fort Leavenworth [Kan.] gathering this information and getting it out to those who need it, from family readiness to forward combat deployments.”

Although a majority of those deployed into combat leave the military at the end of their tours, the retention rate, for both officers and enlisted, has remained at a steady high point despite the ongoing war. While the economy has been cited as the reason for record levels of new recruits, neither that nor bonuses are considered as important to reenlistment as individuals determining that they have found a satisfying career, despite the hardships and danger. And that is despite some 55 percent of today’s enlisted personnel being married, compared to less than 20 percent during Vietnam.

New enlistees, meanwhile, are generally better educated than in the 1990s and considered more committed to the military, knowing they are likely to be deployed to a combat zone. But it is what they will learn from those who already have been there that is seen as continuing to strengthen the capabilities of the future force.

“Whether someone worked out of a FOB  [forward operating base] or was on patrol every day or flew on a helicopter as a door gunner or crew chief, I think it’s important that a recruit hear those experiences from every different aspect of a combat tour,” according to Marine Col. Eric Mellinger, commander of Parris Island (S.C.) Recruit Training Regiment.

“You can go to a VFW and hear war stories – and a lot of them are filled with valor – but that’s not what a recruit needs. A recruit needs to hear, ‘This is the Marine Corps values system and this is how it’s being manifested and demonstrated on the battlefield.’ If you’re just looking for war stories, you can put on Saving Private Ryan.”

Passing along combat experience is not just happening in the active duty force, however. Sgt. 1st Class Brandon E. Reik, for example, served two tours in Iraq with the Washington Army National Guard as a combat engineer clearing improvised explosive devices (IEDs) from convoy routes. Now he helps train other Guard units preparing for deployment.

“I was asked to come here and assist with IED-defeat training and pass along some of the information and events that I went through in real life, in theater, to people who are going there to give them a better understanding of how IEDs work and what the dangers are,” he said. “I am very passionate about it because I feel the knowledge I’ve gained by being there would benefit soldiers that have never deployed before.”

There have been concerns voiced that a professional military with widespread combat experience may have little in common with a general civilian population with little knowledge of or experience with the military. That has been reflected, to some degree, in polls showing the American public is tiring of a war they no longer understand, even as warfighters report they are having success and are proud of the jobs they are doing.

As those combat-experienced warfighters re-enlist, rather than leave the service wholesale for “normal” civilian lives, as did their predecessors from previous wars, the knowledge those earlier warriors shared with their co-workers, neighbors, and families, while now benefiting new military members, is not making its way into the national consciousness to the same degree.

That has been counter-balanced, however, by the massive use of what once were dismissed by the active force as “weekend warriors” – Guard and Reserve members who go through the same training, with the same equipment, and face the same dangers and experiences in combat. Today they have become a vital part of the nation’s total military capability and invaluable future resource, as well as a conduit to the general public on the realities of military service and war.

Since being called to duty after 9/11, the Guard and Reserve have relied on supplemental defense budget requests for their operational funding, rather than being made a line item part of the Department of Defense’s (DoD’s) base budget. The question, according to the Center for New American Security (CNAS), an independent research institution, is whether DoD, Congress, and the executive branch will provide the funding and support needed to keep Guard and Reserve forces at their current level of training, equipment, and expertise.

“Since this supplemental account will vanish as U.S. military operations in Afghanistan and Iraq wind down, the operational functions of the Guard and Reserves – which will prove essential in future missions requiring specialized and high-tech skills – are at risk of disappearing along with it, particularly if overall defense spending tapers off as expected,” warned a September 2010 CNAS report entitled “An Indispensable Force: Investing in America’s National Guard and Reserves.”

Written by CNAS President John Nagl and research associate Travis Sharp, the report called the Reserve components – the Army National Guard, Air National Guard, Army Reserve, Air Force Reserve, Navy Reserve, Marine Corps Reserve, and Coast Guard Reserve – crucial to providing the U.S. military with specialized skills it will need for operations through the next 20 years.

“The Guard and Reserves are at a crossroads. Down one path lies continued transformation into a 21st century operational force and progress on the planning, budgetary and management reforms still required to make that aspiration a reality. Down the other path lies regression to a Cold War-style strategic force meant only to be used as a last resort in the event of major war,” former Army Chief of Staff Gen. Gordon R. Sullivan, now retired, wrote in his foreword to the report.

Nagl and Sharp concluded the report with a call on those in power to recognize and maintain the experience now resident in the Guard and Reserves, in line with the 2008 final report of the congressionally created Commission on the National Guard and Reserves.

“The U.S. government should not allow this opportune moment, when the reserve component’s wartime experience makes it more combat capable than ever before, to lapse without making further progress on implementing the Commission’s unaccomplished recommendations,” they wrote.

“DoD and Congress should address the challenges posed by roles and missions – including homeland response and civil support – readiness, cost, education and the continuum of service by cooperating to strengthen the professional bond between active and reserve component personnel in order to build a more seamlessly integrated total force. Doing so will ensure that the cost-effective National Guard and Reserves can fulfill their role as an indispensable force for defending U.S. sovereign territory and protecting America’s security interests around the world.”

In a February 2010 report on “Keeping The Edge: Revitalizing America’s Military Officer Corps,” Nagl and CNAS research fellow Brian M. Burton voiced similar concerns for the military’s officer corps. The current high operational tempo and prospect of frequent deployments has increased the “pull factor” that traditionally has seen the best officers drawn away to higher-paid civilian jobs, they warned, despite a troubled economy.

“Current officer career paths were built for a very different military than the one we have today. Encouraging the accession and retention of more of the best available talent into the officer corps will require offering more diverse and flexible career paths that encourage risk-taking and unconventional assignments,” they wrote.

“Increased use of sabbatical years – particularly to pursue higher education or gain additional experience in an unconventional assignment, while also allowing ‘downtime’ from deployments for families – would provide additional career flexibility for future generations of officers who will not be satisfied with the military’s current Industrial Age personnel management.”

A third CNAS report, “To Serve the Nation: U.S. Special Operations Forces in an Era of Persistent Conflict,” in June 2010 asked if DoD and the government are taking the actions necessary to fully utilize – and preserve the combat experience of – the nation’s special operators.

Authored by former National Security Council staff member and Senior Director for Combating Terrorism Strategy Michele L. Malvesti, the report noted the strategic and operational interagency relationships the special operations forces (SOF) community has developed, along with the ability to fuse and exploit intelligence analysis with Joint Interagency Task Force operations in the field.

“SOF capabilities for addressing irregular security challenges on non-traditional battlefields are in many ways outpacing the nation’s policies for optimal SOF employment. Accordingly, senior decision makers should undertake a deliberative process that not only accounts for strategic ways to leverage all instruments of national power, but also rationalizes approvals for special operations in these environments,” she wrote.

“As part of this process, it is incumbent on SOF to bring policymakers innovative ways to operate across the 21st century security landscape. Innovation should focus not just on kinetic actions to defeat imminent threats in hot areas, but also on prevention-oriented engagement activities that will stabilize the environment and allow for critical follow-on development aid and assistance in simmering regions of the world.”

In recent months, Secretary of Defense Robert Gates has called for a reduction in overhead and headquarters spending, including reducing the number of active duty generals and admirals. While he has vowed to fight efforts to cut the defense budget, he also has conceded it is unlikely Congress or the administration will approve even a 2 to 3 percent increase considered necessary to maintain the current force in the next few years.

In the executive summary of his 2010 Quadrennial Defense Review, Gates wrote of the need to maintain land, air, and naval forces capable of fighting both limited and large-scale conflicts, while also being prepared to respond to other challenges from both state and non-state groups. In no small part, that capability will rely on the experience of the current corps of officers and NCOs.

“This includes maintaining the ability to prevail against two capable nation-state aggressors, but we must take seriously the need to plan for the broadest possible range of operations – from homeland defense to deterrence and preparedness missions – occurring in multiple and unpredictable combinations,” he wrote, adding that includes creating an environment in which experienced personnel are more likely to remain in uniform, while acknowledging that may not always be possible.

“Operations over the past eight years have stressed the ground forces disproportionately, but the future operational landscape could also portend significant long-duration air and maritime campaigns for which the U.S. armed forces must be prepared. Our preserve-and-enhance efforts will focus on transitioning to sustainable rotation rates that protect the force’s long-term health. The department plans that in times of significant crisis, U.S. forces will be prepared to experience higher deployment rates and briefer dwell periods for up to several years at a time and/or to mobilize the reserve component.”

Being “battle-hardened” by nearly a decade of combat has given the U.S. military an unprecedented level of experience throughout both the enlisted ranks and officer corps – experience that already is being passed on to incoming recruits. But it also has led to a new concern for those who have had multiple deployments – or may have them in the future.

“Yes, soldiers have learned an awful lot about working together in combat, but there also are long-term effects on soldiers and their families, which is one reason, even down to the squad level, there is a serious look at telling individual soldiers ‘Hey, you do need to take a knee here,’” Grady concluded. “Being in combat is a life-changing experience and you do need to take the time to heal yourself.

“In the Army, squad level leaders are now being sent to the University of Pennsylvania to be trained in how to recognize issues that come up with repeated deployments. That is being done with both NCOs and officers, as well, at Fort Jackson, S.C. [the Army’s largest initial entry, basic combat, and advanced individual training center].”

This article was originally published in Defense: Land Forces Edition, Fall 2010.