Vietnam, a nation in Southeast Asia on the eastern edge of the Indochinese peninsula, had been under French colonial rule since the 19th century.

During World War II, Japanese forces invaded Vietnam. To fight off both Japanese occupiers and the French colonial administration, political leader Ho Chi Minh—inspired by Chinese and Soviet communism—formed the Viet Minh, or the League for the Independence of Vietnam.

Following its 1945 defeat in World War II, Japan withdrew its forces from Vietnam, leaving the French-educated Emperor Bao Dai in control. Seeing an opportunity to seize control, Ho’s Viet Minh forces immediately rose up, taking over the northern city of Hanoi and declaring a Democratic Republic of Vietnam (DRV) with Ho as president.

Seeking to regain control of the region, France backed Emperor Bao and set up the state of Vietnam in July 1949, with the city of Saigon as its capital.

Both sides wanted the same thing: a unified Vietnam. But while Ho and his supporters wanted a nation modeled after other communist countries, Bao and many others wanted a Vietnam with close economic and cultural ties to the West.

The Vietnam War and active U.S. involvement in the war began in 1954, though ongoing conflict in the region had stretched back several decades.

After Ho’s communist forces took power in the north, armed conflict between northern and southern armies continued until the northern Viet Minh’s decisive victory in the Battle of Dien Bien Phu in May 1954. The French loss at the battle ended almost a century of French colonial rule in Indochina.

The subsequent treaty signed in July 1954 at a Geneva conference split Vietnam along the latitude known as the 17th Parallel (17 degrees north latitude), with Ho in control in the North and Bao in the South. The treaty also called for nationwide elections for reunification to be held in 1956.

In 1955, however, the strongly anti-communist politician Ngo Dinh Diem pushed Emperor Bao aside to become president of the Government of the Republic of Vietnam (GVN), often referred to during that era as South Vietnam.

With the Cold War intensifying worldwide, the United States hardened its policies against any allies of the Soviet Union, and by 1955 President Dwight D. Eisenhower had pledged his firm support to Diem and South Vietnam.

With training and equipment from American military and the CIA, Diem’s security forces cracked down on Viet Minh sympathizers in the south, whom he derisively called Viet Cong (or Vietnamese Communist), arresting some 100,000 people, many of whom were brutally tortured and executed.

By 1957, the Viet Cong and other opponents of Diem’s repressive regime began fighting back with attacks on government officials and other targets, and by 1959 they had begun engaging the South Vietnamese army in firefights.

In December 1960, Diem’s many opponents within South Vietnam—both communist and non-communist—formed the National Liberation Front (NLF) to organize resistance to the regime. Though the NLF claimed to be autonomous and that most of its members were not communists, many in Washington assumed it was a puppet of Hanoi.

A team sent by President John F. Kennedy in 1961 to report on conditions in South Vietnam advised a build-up of American military, economic and technical aid in order to help Diem confront the Viet Cong threat.

Working under the “domino theory,” which held that if one Southeast Asian country fell to communism, many other countries would follow, Kennedy increased U.S. aid, though he stopped short of committing to a large-scale military intervention.

By 1962, the U.S. military presence in South Vietnam had reached some 9,000 troops, compared with fewer than 800 during the 1950s.

A coup by some of his own generals succeeded in toppling and killing Diem and his brother, Ngo Dinh Nhu, in November 1963, three weeks before Kennedy was assassinated in Dallas, Texas.

The ensuing political instability in South Vietnam persuaded Kennedy’s successor, Lyndon B. Johnson, and Secretary of Defense Robert McNamara to further increase U.S. military and economic support.

In August of 1964, after DRV torpedo boats attacked two U.S. destroyers in the Gulf of Tonkin, Johnson ordered the retaliatory bombing of military targets in North Vietnam. Congress soon passed the Gulf of Tonkin Resolution, which gave Johnson broad war-making powers, and U.S. planes began regular bombing raids, codenamed Operation Rolling Thunder, the following year.

The bombing was not limited to Vietnam; from 1964-1973, the United States covertly dropped two million tons of bombs on neighboring, neutral Laos during the CIA-led “Secret War” in Laos. The bombing campaign was meant to disrupt the flow of supplies across the Ho Chi Minh trail into Vietnam and to prevent the rise of the Pathet Lao, or Lao communist forces. The U.S. bombings made Laos the most heavily bombed country per capita in the world.

In March 1965, Johnson made the decision—with solid support from the American public—to send U.S. combat forces into battle in Vietnam. By June, 82,000 combat troops were stationed in Vietnam, and military leaders were calling for 175,000 more by the end of 1965 to shore up the struggling South Vietnamese army.

Despite the concerns of some of his advisers about this escalation, and about the entire war effort amid a growing anti-war movement, Johnson authorized the immediate dispatch of 100,000 troops at the end of July 1965 and another 100,000 in 1966. In addition to the United States, South Korea, Thailand, Australia and New Zealand also committed troops to fight in South Vietnam (albeit on a much smaller scale).

In contrast to the air attacks on North Vietnam, the U.S.-South Vietnamese war effort in the south was fought primarily on the ground, largely under the command of General William Westmoreland, in coordination with the government of General Nguyen Van Thieu in Saigon.

Westmoreland pursued a policy of attrition, aiming to kill as many enemy troops as possible rather than trying to secure territory. By 1966, large areas of South Vietnam had been designated as “free-fire zones,” from which all innocent civilians were supposed to have evacuated and only enemy remained. Heavy bombing by B-52 aircraft or shelling made these zones uninhabitable, as refugees poured into camps in designated safe areas near Saigon and other cities.

Even as the enemy body count (at times exaggerated by U.S. and South Vietnamese authorities) mounted steadily, DRV and Viet Cong troops refused to stop fighting, encouraged by the fact that they could easily reoccupy lost territory with manpower and supplies delivered via the Ho Chi Minh Trail through Cambodia and Laos. Additionally, supported by aid from China and the Soviet Union, North Vietnam strengthened its air defenses.

By November 1967, the number of American troops in Vietnam was approaching 500,000, and U.S. casualties had reached 15,058 killed and 109,527 wounded. As the war stretched on, some soldiers came to mistrust the government’s reasons for keeping them there, as well as Washington’s repeated claims that the war was being won.

The later years of the war saw increased physical and psychological deterioration among American soldiers—both volunteers and draftees—including drug use, post-traumatic stress disorder (PTSD), mutinies and attacks by soldiers against officers and noncommissioned officers.

Between July 1966 and December 1973, more than 503,000 U.S. military personnel deserted, and a robust anti-war movement among American forces spawned violent protests, killings and mass incarcerations of personnel stationed in Vietnam as well as within the United States.

Bombarded by horrific images of the war on their televisions, Americans on the home front turned against the war as well: In October 1967, some 35,000 demonstrators staged a massive Vietnam War protest outside the Pentagon. Opponents of the war argued that civilians, not enemy combatants, were the primary victims and that the United States was supporting a corrupt dictatorship in Saigon.

By the end of 1967, Hanoi’s communist leadership was growing impatient as well, and sought to strike a decisive blow aimed at forcing the better-supplied United States to give up hopes of success.

On January 31, 1968, some 70,000 DRV forces under General Vo Nguyen Giap launched the Tet Offensive (named for the lunar new year), a coordinated series of fierce attacks on more than 100 cities and towns in South Vietnam.

Taken by surprise, U.S. and South Vietnamese forces nonetheless managed to strike back quickly, and the communists were unable to hold any of the targets for more than a day or two.

Reports of the Tet Offensive stunned the U.S. public, however, especially after news broke that Westmoreland had requested an additional 200,000 troops, despite repeated assurances that victory in the Vietnam War was imminent. With his approval ratings dropping in an election year, Johnson called a halt to bombing in much of North Vietnam (though bombings continued in the south) and promised to dedicate the rest of his term to seeking peace rather than reelection.

Johnson’s new tack, laid out in a March 1968 speech, met with a positive response from Hanoi, and peace talks between the U.S. and North Vietnam opened in Paris that May. Despite the later inclusion of the South Vietnamese and the NLF, the dialogue soon reached an impasse, and after a bitter 1968 election season marred by violence, Republican Richard M. Nixon won the presidency.

Nixon sought to deflate the anti-war movement by appealing to a “silent majority” of Americans who he believed supported the war effort. In an attempt to limit the volume of American casualties, he announced a program called Vietnamization: withdrawing U.S. troops, increasing aerial and artillery bombardment and giving the South Vietnamese the training and weapons needed to effectively control the ground war.

In addition to this Vietnamization policy, Nixon continued public peace talks in Paris, adding higher-level secret talks conducted by Secretary of State Henry Kissinger beginning in the spring of 1968.

The North Vietnamese continued to insist on complete and unconditional U.S. withdrawal—plus the ouster of U.S.-backed General Nguyen Van Thieu—as conditions of peace, however, and as a result the peace talks stalled.

The next few years would bring even more carnage, including the horrifying revelation that U.S. soldiers had mercilessly slaughtered more than 400 unarmed civilians in the village of My Lai in March 1968.

After the My Lai Massacre, anti-war protests continued to build as the conflict wore on. In 1968 and 1969, there were hundreds of protest marches and gatherings throughout the country.

On November 15, 1969, the largest anti-war demonstration in American history took place in Washington, D.C., as over 250,000 Americans gathered peacefully, calling for withdrawal of American troops from Vietnam.

The anti-war movement, which was particularly strong on college campuses, divided Americans bitterly. For some young people, the war symbolized a form of unchecked authority they had come to resent. For other Americans, opposing the government was considered unpatriotic and treasonous.

As the first U.S. troops were withdrawn, those who remained became increasingly angry and frustrated, exacerbating problems with morale and leadership. Tens of thousands of soldiers received dishonorable discharges for desertion, and about 500,000 American men from 1965-73 became “draft dodgers,” with many fleeing to Canada to evade conscription. Nixon ended draft calls in 1972, and instituted an all-volunteer army the following year.

In 1970, a joint U.S-South Vietnamese operation invaded Cambodia, hoping to wipe out DRV supply bases there. The South Vietnamese then led their own invasion of Laos, which was pushed back by North Vietnam.

The invasion of these countries, in violation of international law, sparked a new wave of protests on college campuses across America. During one, on May 4, 1970, at Kent State University in Ohio, National Guardsmen shot and killed four students. At another protest 10 days later, two students at Jackson State University in Mississippi were killed by police.

By the end of June 1972, however, after a failed offensive into South Vietnam, Hanoi was finally willing to compromise. Kissinger and North Vietnamese representatives drafted a peace agreement by early fall, but leaders in Saigon rejected it, and in December Nixon authorized a number of bombing raids against targets in Hanoi and Haiphong. Known as the Christmas Bombings, the raids drew international condemnation.

A top-secret Department of Defense study of U.S. political and military involvement in Vietnam from 1945 to 1967 was published in the New York Times in 1971—shedding light on how the Nixon administration ramped up conflict in Vietnam. The report, leaked to the Times by military analyst Daniel Ellsberg, further eroded support for keeping U.S. forces in Vietnam.

In January 1973, the United States and North Vietnam concluded a final peace agreement, ending open hostilities between the two nations. War between North and South Vietnam continued, however, until April 30, 1975, when DRV forces captured Saigon, renaming it Ho Chi Minh City (Ho himself died in 1969).

More than two decades of violent conflict had inflicted a devastating toll on Vietnam’s population: After years of warfare, an estimated 2 million Vietnamese were killed, while 3 million were wounded and another 12 million became refugees. Warfare had demolished the country’s infrastructure and economy, and reconstruction proceeded slowly.

In 1976, Vietnam was unified as the Socialist Republic of Vietnam, though sporadic violence continued over the next 15 years, including conflicts with neighboring China and Cambodia. Under a broad free market policy put in place in 1986, the economy began to improve, boosted by oil export revenues and an influx of foreign capital. Trade and diplomatic relations between Vietnam and the U.S. resumed in the 1990s.

In the United States, the effects of the Vietnam War would linger long after the last troops returned home in 1973. The nation spent more than $120 billion on the conflict in Vietnam from 1965-73; this massive spending led to widespread inflation, exacerbated by a worldwide oil crisis in 1973 and skyrocketing fuel prices.

Psychologically, the effects ran even deeper. The war had pierced the myth of American invincibility and had bitterly divided the nation. Many returning veterans faced negative reactions from both opponents of the war (who viewed them as having killed innocent civilians) and its supporters (who saw them as having lost the war), along with physical damage including the effects of exposure to the toxic herbicide Agent Orange, millions of gallons of which had been dumped by U.S. planes on the dense forests of Vietnam.

In 1982, the Vietnam Veterans Memorial was unveiled in Washington, D.C. On it were inscribed the names of 57,939 American men and women killed or missing in the war; later additions brought that total to 58,200.