At the end of the Vietnam War the armed forces, especially the Army, are demoralized. They believe the civilian leadership, who had micromanaged the war, helped "break" the U.S. military by alienating and losing career officers, not offering adequate training, and overextending the armed forces.

The lessons the military takes from Vietnam include the need to ensure the American public is behind a war effort and the need to wage a "total war" instead of fighting incremental battles that could lead to a quagmire.

After Vietnam, the military begins a rebuilding phase, establishing a new, all-volunteer Army and creating a heavy force of tanks, a 600-ship Navy, squadrons of new fighters and bombers, as well as new war plans to avoid becoming embroiled in counter-insurgencies.

"We rebuilt the [post-Vietnam] Army for the war we thought we wanted to fight, the war in Central Europe against the Russians, " Col. Douglas Macgregor (U.S. Army-Ret.) tells FRONTLINE. "And we said,'We don't ever want to fight another counterinsurgency. We don't want to go to another place like Vietnam.' And suddenly anything that was different from the World War II scenario in Central Europe was unacceptable. It was another potential Vietnam."

The Carter administration launches a military mission called "Operation Eagle Claw" to rescue Americans held hostage in Tehran following Iran's 1979 Islamic fundamentalist revolution. Poorly planned, the mission is aborted when sandstorms disable three of the eight helicopters. During the evacuation, a U.S. helicopter and transport plane collide in the Iranian desert killing eight soldiers.

The failure of "Operation Eagle Claw" is another post-Vietnam blow for the military. Newly elected President Ronald Reagan launches the largest peacetime defense buildup in U.S. history. During the 1980s, money pours into new weapons systems, such as the M-1 Abrams tank to beef up Army forces in Europe. The Army also forms a rapid deployment force to prepare for possible Soviet threats in places like the Middle East.

The U.S. twice sends troops to Lebanon during the early 1980s following the Israeli invasion of that country. The first deployment of U.S. Marines oversees the withdrawal of the Palestinian Liberation Organization (PLO) from Beirut. In the second deployment, 1,800 Marines join a multinational force to help separate warring Lebanese factions.

On Oct. 23, a suicide bomber detonates a truck of explosives at a Marine barracks near the airport, killing 241 Marines and wounding more than 100 others. It is the largest U.S. death toll in a military operation since Vietnam.

The Beirut bombing becomes a symbol to the military of ill-considered foreign policy objectives and poorly defined rules of engagement. It triggers the development of what becomes known as the Weinberger Doctrine, named for then-Defense Secretary Casper Weinberger. In a Nov. 28 speech before the National Press Club, Weinberger outlines six criteria for deciding whether to commit U.S. troops abroad:

• Any military mission abroad must be deemed vital to U.S. national interests or the interests of U.S. allies;

• The U.S. must commit the forces and resources necessary to win the conflict;

• The political and military objectives of the mission must be clearly defined;

• Combat requirements of the mission should be continually reassessed and adjusted to meet the changing conditions and objectives of the conflict;

• Support from Congress and the American public must be won before committing forces abroad; and

• The use of military force should be a last resort.

Weinberger's military aide at the time, Colin Powell, follows through on Weinberger's doctrine when he is chairman of the Joint Chiefs of Staff during the Gulf War and it becomes known as the Powell Doctrine. But while immensely influential in military circles, Weinberger's doctrine is challenged by others in the Reagan administration. Secretary of State George Shultz is one of many who worry that U.S. diplomacy, not backed up by credible threats of force, will be hamstrung by the military's perceived reluctance to become involved in "limited" wars.

Two days after the Marine barracks bombing in Lebanon, U.S. troops invade the small Caribbean island of Grenada in "Operation Urgent Fury." The mission's purpose is ostensibly to rescue some 600 American medical students who are described as potential hostages of Cuban and Grenadian forces.

Four years earlier, revolutionaries had overthrown Grenada's leader in a bloodless coup, and Cuba and the U.S.S.R. aided the new regime in building up Grenada's armed forces. Tensions with the U.S. increased when it was learned that Fidel Castro sent Cuban workers to help construct an airport. The Reagan administration, believing the airport would be used for military purposes by the U.S.S.R. and Cuba, rejected the Grenadian government's explanation that the airport was for tourism. An early October 1983 coup, which results in the assassination of the Grenadian leader and the ensuing unrest provided the rationale for the Reagan administration to send in troops to protect the American students.

"Operation Urgent Fury" marks the first time since Vietnam that U.S. troops are sent into combat. The military expects an easy operation, but faces greater resistance than anticipated and suffers from serious complications, including disorganization, inadequate intelligence, inter-service rivalries, and poor leadership, particularly within the Army. At least 19 Americans are killed and 116 are wounded in the invasion, which at its height involves 9,600 U.S. soldiers.

With the successful evacuation of the students, the Reagan administration portrays the invasion as a victory. But the military rigorously assesses its failures and decides to reorganize units of the Army's 82nd Airborne Division, retire senior officers, and revise training procedures.

President Reagan orders retaliatory air strikes on targets in Libya, the suspected sponsor of a terrorist attack on a German discotheque popular with off-duty U.S. servicemen that had killed one U.S. soldier and wounded more than 60 other soldiers. Dubbed "Operation El Dorado Canyon," the air strikes involve 200 aircraft and more than 60 tons of bombs.

The surprise action is evidence of the Reagan administration's increasing willingness to use force in pursuit of clearly defined political and military goals -- echoing elements of the Weinberger doctrine.

This act, sponsored by Sen. Barry Goldwater (R-Ariz.) and Rep. Bill Nichols (D-Ala.) fundamentally reforms the civilian-military relationship and is bitterly opposed by the Pentagon.

The goal of Goldwater-Nichols is to strengthen civilian authority in the Pentagon and to unify all the military services during wartime by streamlining the military's chain of command in order to prevent inter-service infighting and improve inter-service communication -- problems that had plagued previous military missions, including Vietnam, Desert One and Grenada.

The law designates an independent chairman of the Joint Chiefs of Staff (JCS) to serve as principal military adviser to the president and defense secretary and report directly to them. (Prior to Goldwater-Nichols, chairmanship of the JCS rotated among the four service chiefs and each chairman was inclined to promote the interests of his own service.) In 1989, Colin Powell becomes the first chairman to serve a full term after passage of Goldwater-Nichols. Capitalizing on the newly defined position, Powell becomes the most powerful JCS chairman ever.

Goldwater-Nichols also transforms the chain of command for the regional combatant commanders, known as the CINCs, by removing the JCS from the chain of command. CINCs now report directly to the defense secretary, who in turn reports to the president. In an attempt to minimize inter-service rivalries, the law also gives the CINCs control over all services participating in its unified command.

Another significant aspect of the Goldwater-Nichols bill is that it requires the executive branch to issue an annual report to Congress outlining its national security strategy.

In February 1988, two Florida grand juries indict Panamanian dictator Manuel Noriega on drug charges. Relations between the U.S. and Panama worsen over the next year. The U.S. imposes economic sanctions and accuses Panama of harassing U.S. military personnel stationed in the country. In October 1989, an attempted coup against Noriega, who had nullified presidential election results, fails. In mid-December, Panamanian soldiers kill an unarmed U.S. soldier, wound another U.S. soldier, and arrest a third soldier and his wife, whom they threaten with sexual abuse.

The U.S. launches "Operation Just Cause" on Dec. 20 to bring Noriega to face justice in the U.S., restore democracy in Panama, combat drug trafficking and protect the 35,000 Americans in Panama. Noriega eventually is persuaded to surrender. In April 1992 he is convicted on racketeering, money laundering and drug trafficking charges and sentenced to 40 years in prison.

The Panama invasion involves more than 20,000 U.S. troops and is the largest military operation since Vietnam. Some critics question the size of the invasion force, arguing that the large buildup prevented U.S. forces from maintaining operational surprise. But as the military's first post-Cold War success story, the mission helps overcome institutional resistance within the Pentagon on the use of military force. It also helps restore the public's confidence in the Pentagon's capabilities. In the first test of the Joint Chiefs' chairman's new role after Goldwater-Nichols, Powell serves as principal military adviser to Defense Secretary Cheney and President Bush. His televised briefings during the invasion are praised; his poise bolsters public confidence and support.

Three days after Saddam's invasion, President George H.W. Bush declares, "This will not stand, this aggression against Kuwait." He sends U.S. troops to the region on Aug. 8.

In the weeks that follow, the president's national security team is divided on going to war against Iraq. JSC Chairman Colin Powell argues forcefully that Bush should rely on economic sanctions and containment against Saddam. By October the president has rejected those arguments.

Internal battles also are fought over the war plan. According to an account in James Mann's book, Rise of the Vulcans, the initial one drawn up by CENTCOM Commander Gen. Norman Schwartzkopf calls for a direct, frontal assault against Iraq forces. When Powell presents it to the civilian principles, they hate it. Defense Secretary Dick Cheney and Defense Undersecretary for Policy Paul Wolfowitz secretly explore a separate war plan, which becomes known as "Operation Scorpion." The plan calls for U.S. troops to attack Iraq's Western Desert from Saudi Arabia, which would allow the U.S. to protect Israel from Iraqi Scud missile attacks (the Scuds had to be launched from the Western Desert to reach Israel because of their limited range) and give the U.S. air superiority over Iraqi troops which were stationed in the northern and eastern parts of the country, as well as the vast majority of Iraqi troops, which were in Kuwait.

Mann writes that Cheney, in an extraordinary maneuver, presents the alternate plan to the president and his National Security Adviser Brent Scowcroft while Powell is out of town in Saudi Arabia. The plan is ultimately set aside; neither the civilian nor the military leaders want the U.S. to create a power vacuum in Baghdad and become bogged down in tensions among Iraq's ethnic groups.

The air war of Operation Desert Storm begins on Jan. 17 and lasts six weeks. On Feb. 24, the ground attack is launched and within days, the U.S. military realizes that the Iraqis are not going to stand and fight. After Powell expresses concern that the allied rout of Iraqi forces will be seen as a massacre, Bush decides to end the war. A cease-fire takes effect at 8 AM on Feb. 28.

For the military, the Gulf War's success restores its self-confidence. It also confirms the Powell-Weinberger Doctrine: The U.S. would only use the military when it was central to national security, and when it was used, it would be done with overwhelming force. As Lt. Col Paul Van Riper (U.S. Marine Corps-Ret.) tells FRONTLINE, "If there's one word that would describe how most of us felt, it was 'vindicated.' Vindicated in the sense that we'd gotten it right between Vietnam and the Gulf War and had gone out on the battlefield and proved it."

Building upon his performance in the media briefings in the Panama invasion, Powell becomes a bona fide media star following his briefings during the Gulf War. As author James Mann recounts, "What you see on the Pentagon podium in the Gulf War is Colin Powell, physically imposing, in uniform, very confident, talking about what the United States is going to do. ... The usual picture is Powell at the podium, Cheney kind of behind him."

But critics, such as Col. Douglas Macgregor (U.S. Army-Ret.), argue there were unintended consequences to the victory in the Gulf War. "What Desert Storm turned out to be for the army, sadly, was what Waterloo was to the British Army," he argues. "After Waterloo had been fought and won, the emphasis was in maintaining the army that they thought had won the Battle of Waterloo in perpetuity, without any reform, without any change, without any structural modification."

See FRONTLINE's report "The Gulf War."

The military develops a new strategy after the Gulf War, known as the two major-theater-war strategy or 2MTW. It requires the military to be ready to fight two simultaneous conventional wars in two different theaters of operation, for example in Iraq and North Korea. Advocates of the strategy believe it is the best way to ensure American military preeminence because it deters potential enemies from challenging the U.S.

Yugoslavia's breakup in 1991 ignites ethnic violence among the region's Serb, Croat and Muslim populations. War breaks out in Bosnia the following year, after it moves for independence. The Serbs' brutal attacks on Bosnia's Muslim population lead to international calls for intervention.

On Oct. 4, 1992, The New York Times publishes a blistering editorial that takes the Powell Doctrine head on. "In short, what Bosnia holds out to the military is the prospect of dangerous, undesirable duty," the editors write. "But when Americans spend more than $280 billion a year for defense, surely they ought to be getting more for their money than no-can-do. It is the prerogative of civilian leaders confronting this historic nightmare to ask the military for a range of options more sophisticated than off or on, stay out completely or go in all the way to total victory."

Four days later, Powell publishes an equally impassioned response in the paper, pointing to the Gulf War and the U.S. invasion in Panama, as well as smaller military interventions in the Philippines, Somalia, Liberia, and other humanitarian relief operations. "All of these operations had one thing in common: they were successful," he writes. "There have been no Bay of Pigs, failed desert raids, Beirut bombings and no Vietnams." The reason for success, he argues, is that all of those missions had clearly defined political objectives -- something lacking in the debate over intervening in Bosnia.

In other words, Powell and the military are asking: What's the exit strategy? How long will it take? What is the risk to our troops?"

Before leaving office President George H.W. Bush agrees to send 25,000 U.S. troops to Somalia in "Operation Restore Hope" to assist with U.N. humanitarian aid for Somalia's famine victims. By June 1993, with Bill Clinton now president, U.S. troop levels are reduced to 1,200 combat soldiers and 3,000 support troops. But as U.N. clashes with local warlords increase, U.S. troops become engaged in policing and peacekeeping operations, including raids to arrest warlord Muhammed Farah Aidid, whose gunmen had killed 24 U.N. Pakistani soldiers.

On Oct. 3, 1993, 115 U.S. soldiers are sent into the Somali capital of Mogadishu on a tip that they'll find Aidid and his top lieutenants. Two Black Hawk helicopters are shot down and U.S. soldiers are trapped in a firefight in the streets of Mogadishu. Eighteen U.S. Rangers are killed and 84 soldiers wounded in the battle. Gruesome televised images of a helicopter pilot's body being dragged through the streets lead to a public outcry in the U.S. President Clinton sends reinforcements, but announces that all U.S. troops will be withdrawn from the country by March 31.

The lessons the military draws from the Somalia debacle seem to reinforce the Powell Doctrine: The U.S. military should not be primarily responsible for nation-building and in order to retain public support for a mission, civilian leaders need to clearly explain the rationale for using U.S. forces.

Throughout the 1990s, the issues of force protection and risk aversion in the use of Special Forces will become issues for the Clinton administration as it debates intervening in the Rwandan genocide, and ethic conflicts in Bosnia and Kosovo.

See FRONTLINE's report "Ambush in Mogadishu"

Campaign questions about Clinton's avoidance of the Vietnam draft and his promise to allow gays to serve in the military get his administration's civilian-military relations off to a bad start. The relationship remains prickly throughout most of Clinton's term in office.

The Army begins developing digitization and modernization initiatives to move the force into the next century and to take advantage of new information-based technologies. It experiments with new division structures, intelligence capabilities and integrated technologies to build a force that can respond to post-Cold War threats.

Meanwhile, during the 1990s, active duty Army forces are being cut by about 40 percent as part of post-Cold War military downsizing.

In the middle of the Rwandan genocide, the Clinton administration unveils a new peacekeeping intervention doctrine, known as President Decision Directive 25, that is the result of a year-long policy review. The document sets out criteria for deciding whether an intervention serves U.S. national interests.

According to PDD 25, "The U.S. will support well-defined peace operations, generally, as a tool to provide finite windows of opportunity to allow combatants to resolve their differences and failed societies to begin to reconstitute themselves." Other conditions include: operations that are linked to "concrete political solutions;" specified timeframes that are tied to the political solutions; a strategy that integrates political, military and humanitarian efforts; and a firm budget estimate.

Three years earlier, in 1991, during the first Bush administration, the democratically elected president of Haiti, Jean-Bertrand Aristide, is overthrown by a military junta. The Bush administration debates a response; according to Colin Powell's memoirs, when asked by Defense Secretary Cheney about his opinions on whether the U.S. should use force to restore Aristide to office, Powell replies, "We can take over the place in an afternoon with a company or two of Marines," but warns that getting out may be problematic, noting that the last time the U.S. had intervened in Haiti, its troops stayed for 19 years. As a presidential candidate, Clinton makes an issue of Haiti, promising that he would reverse the Bush administration's policy of inaction.

The violence in Haiti worsens over the next few years and in October 1993, just a week after the ambush in Mogadishu, Somalia, Clinton sends U.S. troops to Haiti on the USS Harlan County to assist in U.N. nation-building projects. However, Lt. Gen. Raoul Cedras, the leader of the military junta, refuses to let the ship dock in Port-au-Prince, and the Clinton administration is embarrassed when the ship is forced to withdraw.

Though the Pentagon is cautious about action in Haiti, the Clinton administration develops an invasion plan involving 25,000 troops. A last-minute deal brokered by former President Jimmy Carter allows Aristide to be restored to power and U.S. troops to go ashore unimpeded by the Haitian military and police.

Haiti is the Clinton administration's first foreign policy victory and most U.S. troops are withdrawn within a year, though several hundred stay for peacekeeping and humanitarian work. However, some critics, such as Max Boot, describe Haiti as a "hollow victory." "Not surprisingly, a mission designed above all to minimize casualties accomplished little else," Boot writes in his book The Savage Wars of Peace, noting that the political situation in Haiti deteriorated in the ensuing years.

The Bosnia conflict enters its third year, and following a deadly bombing of a Sarajevo marketplace by Serbs, NATO forces launch the largest military action in the alliance's history. Two weeks of air strikes, combined with a strong Croat-Muslim offensive on the ground, push Bosnian Serbs to the negotiating table. In November, the factions meet for peace talks in Dayton, Ohio.

The success of the NATO strikes appears to support U.S. civilian leaders' position that limited military attacks can serve as a tool for "coercive diplomacy." The NATO air strikes are approved after years of painstaking negotiations with allies and the U.S. military, which was reluctant and fearful of being drawn into a quagmire, while the warring in Bosnia raged on.

In a speech at George Washington University, National Security Adviser Anthony Lake outlines a series of principles on when and how the U.S. should use military force.

Lake cites seven circumstances that taken "in some combination or even alone," may call for a U.S. military intervention:

• to defend against direct attacks on the U.S., U.S. citizens and allies;

• to counter aggression;

• to defend key economic interests;

• to preserve, promote and defend democracy;

• to prevent the spread of weapons of mass destruction, terrorism, international crime, and drug trafficking;

• to maintain "reliability" with the international community, "because when our partnerships are strong and confidence in our leadership is high, it is easier to get others to work with us, and to share the burdens of leadership;" and

• for humanitarian purposes.

He also argues that three principles should be considered when deciding how to use force:

• Threatening to use force can often achieve the same results as using force, provided that the political and military leadership is prepared and ready to carry through on the threat;

• A "selective but substantial" force may sometimes be more appropriate than a massive use of force, so long as the force is adequate to accomplish the mission;

• A clear exit strategy is essential.

In the speech, Lake points to the Clinton administration's achievements in Bosnia and Haiti as successful operations that meet the above circumstances and principles.

Ethnic tensions in Kosovo flare in 1991 following Yugoslavia's breakup and Kosovo's growing crisis is not resolved in the Dayton Accords that end the war in Bosnia. By 1998, the region erupts in a cycle of violence between Serbs, who revere Kosovo as the sacred ground of their ancestors, and ethnic Albanians, who live there and have chafed under Serbian oppression.

NATO launches "Operation Allied Force," a war against Serbia to prevent Serbian President Milosevich from deporting or destroying Kosovo's Albanian population. NATO's war is led by U.S. Army Gen. Wesley Clark. But from the beginning, the mission is hampered by the Clinton administration's and Pentagon's unwillingness to take casualties, and by the need to maintain consensus among NATO's political leaders.

NATO's leaders decide that they will fight a war of limited air strikes, with jets flying three miles high to minimize the possibility of pilots being shot down. From the start, ground forces are ruled out: The night the war begins President Clinton announces ground troops are off the table, stating: "I do not intend to put our troops in Kosovo to fight a war." This angers NATO's generals.

Because discord within NATO could cripple the alliance, the air strikes are limited to targets approved by NATO consensus. After three days, the strikes have hit all such targets and NATO military leaders want to strike Belgrade next. But NATO's European allies are uncomfortable with televised images of the bombing of a European city. In the end, the allies reluctantly agree and NATO bombers begin striking Belgrade on April 3, with the politicians insisting on approval and veto power over the targets.

One mission during the Kosovo conflict, known as "Task Force Hawk," comes to symbolize the Army's risk-averse nature and convinces both civilian and military leaders of the need for change. Because NATO's jets are hampered by bad weather and rough terrain, Gen. Clark pushes the Army to send Apache helicopters, its most fearsome attack weapon. He meets fierce resistance in the Pentagon, where senior leaders predict the Apache units would suffer 50 percent casualties. The Army finally sends two-dozen helicopters but insists on sending 6,200 troops and 26,000 tons of equipment to support the Apaches at a base that is specially constructed for them in Albania. The equipment, including tanks, is too heavy to move in the waist-high mud of local roads.

On May 4, during Task Force Hawk's first training missions, two of the Apaches crash into a hillside and two pilots are killed. The Apaches are grounded by the Pentagon and never used in the Kosovo War.

After 78 days of bombing, the Kosovo war -- the first war to be won by air power alone -- ends on June 10, after Milosevic agrees to withdraw Serbian troops from Kosovo.

Read a detailed chronology of the war in Kosovo and more on the lessons of "Task Force Hawk."

As Army Chief Eric Shinseki told FRONTLINE in an interview conducted in 2000, a factor in his decision to pursue transformation is the lessons that were learned from "Task Force Hawk " in Kosovo.

Shinseki's vision to remake the Army for 21st-century wars involves developing a new medium-weight force capable of deploying anywhere in the world in 96 hours. While developing the medium-weight forces, he would maintain the current Army forces and focus on aggressively designing a new, high-tech Army called "the objective force" by 2012-2015. Shinseki also begins efforts to train two new brigades at Ft. Lewis, Washington, using wheeled vehicles instead of the traditional heavier-tracked armored personnel carriers.

The career military, which tends to vote Republican by a large margin, is pleased to see a Republican administration take office after eight years of the Clinton administration. According to Washington Post reporter Tom Ricks, "A large number of retired generals had endorsed Bush and Cheney in the election, and there's a lot of buy-in to phrases like,'We'll have adults running the place again,' and so on."

During the campaign, candidate George W. Bush argues the military is overly burdened by overseas commitments and he opposes using the military for nation-building exercises. He also promises pay raises and improved benefits for the armed services.

Bush appoints Donald Rumsfeld secretary of defense. A former Navy pilot, he was also secretary of defense in the Ford administration.

In his first months in office, Rumsfeld's primary goal is to reassert civilian control over a Pentagon that had been dominated by the uniformed military during the Clinton years. He announces a top-down review of Pentagon policy and seizes the military promotion process, personally interviewing three- and four-star candidates.

Convinced that they are blocking innovation, Rumsfeld targets the permanent Pentagon bureaucracy, and in particular Gen. Shinseki and the Army, which he believes is lumbering and intransigent. Some uniformed military complain about their treatment by Rumsfeld, including Chairman of the Joint Chiefs Hugh Shelton, who tells Washington Post reporter Dana Priest that he is being treated "like a second-rate citizen."

Rumsfeld develops his own views on transformation, which involve cutting funding for heavy equipment and developing a high-tech military that relies on fewer troops. "Donald Rumsfeld wanted to build a smaller, nimbler and more networked military that could respond swiftly to threats anywhere in the world," recalls John Arquilla, a professor at the Naval Postgraduate School.

The uniformed military responds by hunkering down to protect pet projects. Members of Congress, kept in the dark about Rumsfeld's plans, are concerned about how their districts might be affected by the cancellation of defense projects or the deactivation of units.

During the quiet summer of 2001, Rumsfeld's battles appear to be taking a toll. In one of Washington's favorite parlor games, insiders speculate over which Cabinet member will be the first to leave. Rumsfeld is a popular choice.

Rumsfeld argues that Sept. 11, in which the U.S. was attacked by an unconventional, non-state enemy, proves that the Powell Doctrine is irrelevant and that military transformation is essential.

The Quadrennial Defense Review (QDR), conducted every four years, is largely completed before the Sept. 11 attacks, but the Defense Department argues that "these attacks confirm the strategic direction and planning principles that resulted from this review."

The document outlines four pillars and six goals for transformation. The pillars are:

• Strengthening joint operations by developing lighter, more lethal, and readily deployable joint forces;

• Experimenting with new approaches to warfare, operational concepts and capabilities through wargaming, simulations and field exercises focused on emerging challenges and opportunities;

• Exploiting U.S. intelligence advantages by optimizing human intelligence, exploiting emerging technologies, and integrating information from multiple intelligence and open sources; and

• Developing transformational capabilities through investments and innovations in science and technology.

The Defense Department establishes six operational goals for transformation in the report:

• Protect the U.S. homeland and critical bases of operation;

• Deny enemies sanctuary;

• Protect and sustain power in access-denied areas;

• Leverage information technology to connect troops and their operations;

• Improve and protect information networks from attack; and

• Enhance space operations.

In outlining the vision for force transformation, the document states that U.S. forces will be sized and shaped to achieve several goals: defending the U.S.; deterring aggression; defeating aggression in "overlapping major conflicts while preserving for the president the option to call for a decisive victory in one of those conflicts," (as opposed to the two major-theater-war scenario) and conducting a limited number of smaller-scale contingency operations.

After 9/11, CENTCOM Commander Gen. Tommy Franks tells an unhappy Secretary of Defense Donald Rumsfeld it will take months to move U.S. forces and plan an attack on the Taliban and Al Qaeda in Afghanistan. But the CIA has its own plan, which is soon approved. It calls for the agency's paramilitary officers to link up with Afghan guerillas to attack Al Qaeda and the Taliban. Rumsfeld is chagrined the U.S. Army is left out, but he manages to attach Special Operations forces to the war plan.

The Afghanistan campaign -- in which CIA paramilitary operatives buy off the warlords and get the various Afghan factions to unite, while 12-member teams of Green Berets join up with the Afghans and use laser guidance systems to direct B-52 air strikes on targets -- is seen as a success and reinforces Rumsfeld's views on transforming the lumbering Army.

The campaign adheres to the Powell Doctrine tenet of overwhelming force, but in a new way. "People tended to think of overwhelming force as lots of Army boots on the ground," says The Washington Post's Thomas Ricks. "What Rumsfeld, I think, grasped very quickly because he does have a technological orientation in many ways on military operations is, overwhelming force might be two guys on the ground with a radio and a B-52 overhead."

Read a detailed chronology of the war in Afghanistan.

A few days before Thanksgiving, President Bush secretly asks Rumsfeld to review U.S. war plans for Iraq. Rumsfeld, in turn, asks CENTCOM Commander Gen. Tommy Franks to look at the plans.

The war plan on the shelf for Iraq is based on the success of Desert Storm and calls for weeks of heavy air bombardment and seven months of planning time to build up the troops. Over the next few months, Rumsfeld pushes Franks to revise the plan by thinking outside the box.

Looking for fresh ideas, Rumsfeld asks Col. Douglas Macgregor, a tank commander in Desert Storm and a well-known military maverick, for his ideas for Iraq. Macgregor's plan is for a force of 50,000 troops to be rapidly deployed to strike at the heart of Baghdad.

But career military officers resist such a small invasion force. Gen. Shinseki's position is Army doctrine: A large number of forces is required to secure a country after a conflict. As Gen. Joseph Hoar (U.S. Marine Corps-Ret.), who commanded CENTCOM from 1991-1994 told FRONTLINE, "If you're going to go in and change a country of 25 million people, you've got to have boots on the ground."

The more the generals dig in, the harder Rumsfeld pushes to reduce troop size, getting personally involved in the planning. As The Washington Post's Ricks recalls, " I've heard stories again and again of Rumsfeld actually crossing off individual units from deployment plans saying,'You really don't need this. You don't need this.'" Some generals resented the civilian involvement, recalling the role of the civilian leadership in Vietnam.

When the war plans are finalized, 10 months later, the new plan calls for a force of 140,000 -- far fewer than the uniformed military desired, but far more than the 50,000 proposed by Macgregor. The war would have a rolling start in Kuwait with a rapid deployment to Baghdad.

"I think the plan was less transformational and daring than Rumsfeld hoped it would be," Washington Post reporter Bob Woodward told FRONTLINE. "It was a hybrid. It was a lot of the old and some of the new, probably more of the old than Rumsfeld would like to acknowledge."

Throughout 2002, the Bush administration internally debates how to interrogate hundreds of Al Qaeda and Taliban detainees captured in Afghanistan. Rumsfeld wants the prisoners to be aggressively interrogated, but he and civilian lawyers meet resistance from the military's lawyers, the Judge Advocate General Corps (JAGs), who are trained in the rules of the Geneva Conventions and the Uniform Code of Military Justice, the military's strict standards of behavior.

As required by the Goldwater-Nichols Act, the Bush administration releases its National Security Strategy. Although it does not include any specific military guidance, the 33-page document, which becomes known as the "Bush Doctrine," presents a bold and comprehensive reformulation of U.S. foreign policy. It outlines a new and muscular American posture in the world -- a posture that will rely on preemption to deal with rogue states and terrorists harboring weapons of mass destruction. It states that America will exploit its military and economic power to encourage "free and open societies." It states for the first time that the U.S. will never allow its military supremacy to be challenged as it was during the Cold War. And the NSS insists that when America's vital interests are at stake, it will act alone, if necessary.

Read a chronology that describes the evolution of the Bush Doctrine.

Three weeks before the invasion of Iraq is to begin, Gen. Shinseki is forced to take his internal fight with Rumsfeld public in testimony before the Senate Armed Services Committee. Responding to a question from Sen. Carl Levin (D-Mich.) about the size of the force required for an occupation of Iraq, Shinseki responds:

I would say that what's been mobilized to this point, something on the order of several hundred thousand soldiers, are probably, you know, a figure that would be required. We're talking about post-hostilities control over a piece of geography that's fairly significant with the kinds of ethnic tensions that could lead to other problems. And so, it takes significant ground force presence to maintain safe and secure environment to ensure that the people are fed, that water is distributed, all the normal responsibilities that go along with administering a situation like this.

Rumsfeld and Deputy Defense Secretary Paul Wolfowitz respond with public rebukes of Shinseki. Rumsfeld calls Shinseki's estimates "far from the mark," and Wolfowitz comments two days later in testimony before the House Budget Committee, "First, it is hard to conceive that it would take more forces to provide stability in a post-Saddam Iraq than it would take to conduct the war itself and to secure the surrender of Saddam's security forces and his army -- hard to imagine," he said. Wolfowitz also argues that the Kurdish northern third of Iraq had been liberated from Saddam after the Gulf War and that the area had stayed relatively stable without the presence of U.S. troops.

Approximately 200,000 U.S. forces invade Iraqi. Three weeks later, Baghdad falls. But it is soon evident that there is no postwar planning for the looting, violence and civil unrest that follows the invasion.

Read a detailed chronology of Operation Iraqi Freedom.

The Transformation Planning Guidance outlines the Defense Department's three-part strategy for ensuring "U.S. forces continue to operate from a position of overwhelming military advantage in support of strategic objectives."

The three parts are: transforming the military's culture through leadership that promotes and encourages innovation; balancing the needs of current operations against the strategic investment needed to support future operations; and transforming the force, as described in the 2001 Quadrennial Defense Review.

With thousands of Iraqis arrested and imprisoned, stunning pictures surface of American abuse of Iraqi detainees at the Abu Ghraib prison. What has happened at the prison is similar to what the JAGs were predicting a year before when they were battling Rumsfeld and civilian lawyers over rules of treatment and interrogation.

But Abu Ghraib also comes to symbolize something much larger. "The real significance of Abu Ghraib," says Dana Priest of The Washington Post, is that it's a symbol of the unpreparedness of the military to deal with the chaos and the insurgency of the post-war period. They did not think they would be running prisons, so they had nobody to run the prisons."

As the year ends, roughly 135,000 troops are still in Iraq. As the Washington Post's Thomas Ricks points out, "It is the first sustained ground combat the U.S. mililtary has fought with a volunteer force in over 100 years."

By autumn of 2004, the initial looting and chaos that erupted in the immediate aftermath of the March 2003 invasion has spawned an increasing insurgency against coalition forces and the U.S.-backed Iraqi government. With mounting casualties in Iraq and without a clear exit strategy in either Iraq or Afghanistan, Rumsfeld's critics charge the Secretary Rumsfeld has pushed too far. The danger, they say, is a military incapable of effectively fighting the next major conflict.