The Vietnam War was the first war in modern United States history in which there was large portion of the population opposed America's participation. The was started small, as did the protests. Initially only a few people spoke out against the war, primarily pacifists who are against all wars. Americans were accustomed to fighting wars that were easy to define-but for Vietnam, any definitions or rationalizations were hazy at best. They had a hard time finding a good reason to justify all the lives being lost, especially when many felt that the country's welfare was not directly at stake. Another thing that contributed to people's discomfort with Vietnam was the fact that for the first time, they were actually able to see images of dead people on their TVs, and this affected their beliefs greatly. As the war escalated, so did the number and kind of people who came to oppose it. Opponents came intellectuals, politicians, professors, students and their parents, flower children, and radicals. The first rallies against the war were very small, and had very few people. As the war progressed, the rallies grew to enormous size, even up to over a quarter of a million people, nearly as many as the number of American soldiers in Vietnam. Anti-war events included not only rallies, but moratoriums, concerts, theater performances, and sit-ins. Not all protests were peaceful and some resulted in violence such as the Chicago Demonstrations. There were also acts against the government. For example, raiding Selective Service Offices, the ones responsible for picking who was drafted, and stealing and publishing classified information. The sheer number of people and number of events against the war played a part in America's withdrawal from Vietnam.

Vietnam had been a French colony up to the 1950's, until the French were driven out by communist forces. In order to prevent the whole country from becoming communist, the United States and other democratic countries agreed that it should be divided across the middle, making two countries. From then on, North Vietnam was a communist country, and South Vietnam was "democratic", and supported by Western nations. North Vietnam rebels started attacking South Vietnam, trying to take over the country and add it to the communist empire. The U.S. had been sending over political consultants from the start, but by the early 1960's, President Kennedy started sending over troops to engage in combat. In August of 1964, Congress passed the Tonkin Gulf Resolution, which gave the president, Lyndon Baines Johnson, the power to use whatever force he considered necessary. At year's end, there were 23,000 soldiers fighting in Vietnam. By the end of 1965, the U.S. forces had increased to 385,000. Forces steadily increased over the next two years to a peak of 536,100 in 1968. America had made no progress in securing South Vietnam against the Northern rebels, and the American people were tired of the war. President Nixon began withdrawing forces, until America and North Vietnam reached a tentative agreement to end America's involvement in the war in 1972, although the South Vietnamese kept fighting with U.S. financial help. The peace negotiations took several years during which Congress gradually cut off money to South Vietnam and the "war" officially ended (war was never officially declared, so it never officially ended, although it is recognized as a war). In the end, despite the many lives lost, North Vietnam was victorious and took over South Vietnam in 1975.

As American involvement in Vietnam grew, an increasing number of American soldiers were killed or injured. As these numbers grew, so did the resistance against the war. First it was just the people who were pacifists by belief that were against the war, but as word spread, the Vietnam anti-war movement became the biggest in U.S. history, encompassing many different people.

One group that was against the war was the religious pacifists, who reject violence based on religious principle. Some of the well-known groups that teach pacifism are the Quakers, Mennonite, and the Brethen, as well as Jehovah's Witness and Sufists, who belong to a branch of Islamic teaching that says all evil can be overcame with tolerance and love. The religious pacifists that were most active in working against the war were the Quakers, and they were soon joined by members of other mainstream religions, like Father Daniel Berrigan of the Roman Catholic Church. Another set of pacifists strongly against the war were the humanitarians, who did not go by religious teaching or beliefs. They believe that the most important thing is human life, and nothing is of higher value or importance. They believed that nothing is worth sacrificing human life for and war cannot be justified.

There were other groups who were not opposed to war on principal but were against America's participation in the Vietnam War. This included liberal politicians, such as Eugene McCarthy, as well as notable public figures. Also active against the war were liberal intellectuals such as Daniel Ellsburg. Colleges were hotbeds for anti-war activity because many were very liberal and because the college students were of "draftable" age. Many professors from universities and colleges across the country joined their students' protests against the war. Even parents of these students joined in the protests, as they saw the increasing possibility of their sons being killed in this war.

The last of pacifists were the hippies, or "flower children". When you think of anti-war protesters, the hippies are usually who come to mind. They were a more youthful crowd, who did not want to participate in their parents' culture, which they saw as materialistic and confining. Like traditional pacifists, they preached non-violence, talking of the power of love to overcome to power of guns. They expressed their views through art and music. More politically oriented hippies were called "yippies".

In addition to these others, intensely political groups also protested against the war, such as the Students for a Democratic Society. They belonged to a group called the New Left, which believed that the United States was taking over France's old role in overseeing Vietnam. They also wanted to overturn America's economy as well as end the war in Vietnam. Groups like these were not pacifist at all, sometimes resorting to terrorist-like tactics. One revolutionary group, the Weathermen, set off bombs on the University of Wisconsin campus, as well as other places.

The most popular way to protest against the war was a rally or a march, where people gathered together and chanted and demonstrated against the war. There were also sit-ins, where many people would come together and basically just sit for a long time in order to show their feelings against the war. The more radical groups staged more outlandish things-bombings, for example, to really convey their anti-war feelings. In 1962, a peace demonstration in Washington, D.C. only gathered a few hundred students. By December of 1964, the first nationwide protest against the war was being staged. In late 1965, another demonstration in Washington, D.C. had as many adults as students in attendance. Anti-war feelings continued to grow and become more and more accepted. By 1967, Eugene McCarthy, an anti-war democratic Senator was running for president, and gathered 40% of the New Hampshire primary, a normally conservative state. This victory convinced Johnson, the current president, not to try for a second term. Instead, the Democrats chose Hubert Humphrey, the vice president, as their nominee. At the Democratic National Convention in Chicago, things turned less peaceful as "yippie" demonstrators protested, outraged that Eugene McCarthy was not the nominee. Even as the war was winding down, protests continued. The biggest anti-war demonstration of all took place on October 15th, 1969 when millions of people from all walks of life took place in a nationwide moratorium, a kind of mini-strike in which instead of working, everyone protested somehow. The next month over a quarter of a million people marched on Washington, D.C. The peace movement had grown from a few hundred to millions in only seven years.

As the war grew, more people ended up opposing, for a variety of reasons. As casualties mounted, it became harder to justify supporting the war when there was no clear meaning behind it. Therefore, millions of people who had never questioned thier government joined with others in a wide range of protests. Whatever their feelings, the united effort was part of the reason America withdrew from Vietnam. The Vietnam War had struck such a chord in American society that a nation that had long honored its military and supported its government turned against it.