Well, a number of reasons. Perhaps the most notable, besides the loss/tie difference that you pointed to, is that they were sold as similar wars but were in fact very different. Korea, while unpopular, was nowhere near as catastrophic from a PR point of view as Vietnam. South Korea was a legitimate state, and as such it made sense and was more understandable for the US to intervene on behalf of an endangered ally. The situation in Vietnam was totally different. (Sorry about that, I don't have the sources with me to back that up, so I'll retract it, and I don't know enough about South Korea to answer off the top of my head. My reasoning was based on Diem's ultimately dying in a coup during the war, while See stayed in power afterwards, so I guess stability would be my one word answer.) It seems, at first, exactly like you described, "to protect democratic factions in the country against Communist ones," or protect the South from the North like in Korea. That's the one sentence, official answer, and the one that you're most likely to get from any simple history of the subject. However, the situation in Vietnam was totally different from that sort of ideal. In reality, there was no democratic South Vietnam. It was established after the Geneva Conference of 1954 (which followed Vietnam's war of independence from France) as a temporary state in preparation for national elections in 1956.

Ho Chi Minh, the leader of North Vietnam, was extremely popular, representing both nationalism and successful resistance to a much more powerful foreign occupier, which is something of a recurring theme in Vietnamese history. He was a brutal autocrat, to be sure, frequently killing political opponents, by the thousands if need be. That said, he was not the agent of some larger Communist conspiracy. He played the Soviets for military support during both wars, but did not answer to them, and was a revolutionary nationalist who happened to be Communist rather than a revolutionary Communist seeking to cause the fall of Southeast Asia.

In the leadup to 1956, it was clear that Ho was going to sweep the elections. He was much more popular than his Southern counterpart, Ngo Dinh Diem, who was also autocratic and led an extremely corrupt South Vietnamese (SVN) government, without popular support. By all accounts, South Vietnam should have ended in 1956, with the country unifying after Ho's inevitable victory in the national elections. However, Diep did not partake in the elections, ensuring the prolongation of the SVN state, which thereafter existed almost solely because of US aid.

The question of whether the US should have intervened is an extremely loaded one, but it boils down to a set of assumptions that policy makers had. First, those in charge assumed that Ho was part of a larger Communist plot and that he thus had to be stopped to halt Soviet expansion. Now, the theory of monolithic Communism, which was also key to the domino theory of one country's fall engendering a worldwide collapse of free societies into Communist control, was demonstrably false (Here, I was pointing mainly to Tito being independent and the emergent Sino-Soviet split, which while it was later than the earliest military advisers, still was a political reality at during escalation), and many policymakers knew that. There was no real international agenda, and different countries, whether the USSR, China, Yugoslavia, or Vietnam, had their own take on how to govern and their own priorities.

Second, policymakers assumed that SVN was a viable, independent and preexisting state, which was untrue. It was corrupt, lacked popular support, and should by all rights have disappeared after the 1956 elections. The continued to funnel money and supplies into the government long after they knew that none of it was being put to good use (this appears in both Appy and the Pentagon Papers. Appy says that SVN citizens were well aware of and hated the governmental corruption, and specifically that "Diem's popular support was thin, his military largely inept, his government riddled with corruption." The Pentagon papers also fully acknowledge Diem's unpopularity and inefficiency).

Lastly, Americans assumed that the Vietnam situation would affect their place in international politics as a whole. The whole doctrine of "credibility" led policymakers to think that a fall of SVN to Communism would lead the USSR and the world in general to lose respect and fear for the US, which singlehandedly explains why the war dragged on as long as it did. No one wanted to be the first American president to lose a war, and so they supported the stalemate in the hopes of kicking the can further down the road.

Now, to fully answer your question, basically the war was fought on false premises AND the American public found out about it. Journalists became more critical of American presence as they found out more about the situation. In addition, the publication of the Pentagon Papers, a collection of classified documents concerning American involvement in Vietnam, turned more Americans against the war, and led to an increasingly popular sentiment that this war was being fought for thoroughly wrong reasons, was costing thousands of American lives, was being fought wrong, and that Americans had no real stake in the outcome. Combine all that, and you get the least popular conflict in American history. However, this history is being forgotten at an alarming rate, with support for the Vietnam War increasing the number of Americans who think intervention was a mistake decreasing later and later after the war's end (this was a statistic that I saw, must have simply misremembered it, thanks).

Now, I'm only a college student, and so this likely isn't a perfect answer. I would like to keep contributing to this sub, so feedback is welcome and appreciated.

In terms of sources, this is primarily in James Patterson's Grand Expectations, The United States: 1945-1975 which is a solid general history of recent America, and Christian Appy's Patriots: The Vietnam War Remembered from All Sides which is a fascinating collection of firsthand accounts from people involved with the war, which I cannot recommend highly enough. If you're interested, I would also look into the Pentagon Papers themselves, which, once you're more acquainted with the history behind them, provide a fascinating insight into what happened, and what went wrong.

TL;DR: War fought for wrong reasons, Americans find out about it.

EDIT: Sweet Jesus this blew up, some great comments below, so listen to those smarter people first. I'll try to fix what I can, though there is some stuff that I don't have answers for.

Listen up everyone. We've already have 8 comments which had been deleted for breaking our rules. Unless you can answer this question in-depth and be prepared to answer follow-up questions (and source requests), please refrain from writing. We're not interested in your personal opinion or personal anecdotes. For more information, please read our rules or get in touch with us directly through mod-mail.

I think your question makes the assumption that Korean war was popular. If you look at the polls here you can see that at least at those points in time in 1951 and 1952 it was actually unpopular. Even on a similar level to Vietnam. I know those are just single data points but just trying to question the underlying assumption.

I'd also like to know why they turned out so different, what'd we do differently in Korea?

As far as I can tell, the Korean War came at a time when people were a bit war weary after WW2 and did not really want anything to do with the Korean War. It was not a spectacular war like Vietnam with helicopter combat and the suchlike, but more a form of trench warfare that stalemated fairly quickly around the 38th parallel. To me, it is a highly interesting war, but I think to the majority of Americans, it was not. Also, it was not shrouded in secrecy and dirty dealings like Vietnam. It was a genuine war very early on in the Cold War (Russia did not even have a nuke when it started), unlike Vietnam which was after the chaotic events of the Cuban Missile Crisis. Moreover, the social climate was different. The 1950s were a time of prosperity and generally, people were happy. The 1960s saw the rise of the peace movements and Civil Rights movements. People were challenging the government in multiple ways and when the shady dealings around the start of the war and the operations into Cambodia and Laos came to light, it caught on with the American public.

Sources: Max Hastings, 'The Korean War' and Anthony Salmon 'To The Last Round'. I will add the sources for my knowledge on Vietnam in a minute, but 'We Ain't What We Ought To Be' by Stephen Tuck covers the correlation between the Civil Rights movement and the protests against Vietnam quite nicely.

TL:DR Vietnam is tainted by the people involved, the administrations most remembered for fighting it are Nixon and Johnson. Johnson was said to have lost the war and Nixon to have continued the war in spite of the obvious.

In 1965 when ground troops were introduced and up until the Tet Offensive of 1968 most Americans believed the US to be "winning the war". Body counts were included in news reports to show the numbers as clearly a win in the American column. American had air superiority and could report massive tons of bombs being dropped on Northern targets. In effect there was a wow effect to all of this which was dashed when the entire south was attacked by an enemy that had been tagged as "losing" recently before the attacks in January of 1968. Walter Cronkite calling the war a futile effort struck a chord with the American people.

The other half of the war was managed by Nixon and Kissinger who pulled troops out slowly even as support continued to evaporate in opinion polls and as events such as Kent State and My Lai played out across the public sphere. Kissinger and Nixon approved targets personally, and could be held responsible for mistakes such as the Christmas bombings in 1972 in which many civilians were killed. Basically the argument can be made and has been made that Kissinger and Nixon fought for a peace that Americans could stomach for 4 more years only to get more people killed (Vietnamese civilians and US personnel) for a war that was considered that it would not be won.

In conclusion I think Americans that lived through the war and wrote about it after were influenced by the characters of the people who prosecuted the heaviest involvement from 1965 to 1972. The semi live coverage of the war on the nightly news combined with more color journalism provided people with a colorful backdrop and in depth coverage of characters including Robert MacNamara, Henry Kissinger, and General Westmoreland outside the presidency led to an easier to identify cast of personal villains than Korea.

Sources: Probably being overly influenced by the 6 hour mini series Vietnam in HD I just finished last week, my recent trips to the Life Magazine Photo exhibition at the War Remnants Museum in Saigon, Robert MacNamara's 'In retrospect', CBS News Vietnam War documentaries, 'Dear America: Letters home from Vietnam', the section detailing the Paris Peace Negotiations in Kissinger's "Diplomacy", the Vietnam War with Walter Cronkite.

Most of the best points have already been brought up, but one more:

Calling the Korean War a "tie" is a bit misleading. The North, which invaded first, held nearly the entire peninsula at one point in the war. When hostilities ceased, the the boundaries were back to where they started. That's not really a "tie" — because in terms of territory, the North Koreans' advance was completely halted. They gained nothing, as opposed to gaining everything. My point, in short, is that the difference in "victory level" between Korea and Vietnam was very big.

A lot of people also forget that America was not the sole combatant in Korea. The forces defending South Korea were UN soldiers comprised of 15 nations, the majority were Americans and the UN soldiers were led by MacArthur. It wasn't "America vs. the Commies" similar to Vietnam, a large portion of the world saw the invasion of South Korea as morally wrong, legitimatizing the conflict. As others already said, media coverage was not as comprehensive in Korea as it was in Vietnam either. I'm not a historian or published by any means, but I spent a few months writing this paper (sorry for pastebin, don't know where else I should put it, if anyone actually cares to read it I'd just copy it and paste it into a word processor)

Source for statements made about Korea

The Korean War was a conventional war in the sense that there were clear objectives, an obvious opponent, and a moral sense of right in the US' and UN's actions to aid the South Koreans when the North Koreans invaded with the aid of the USSR and Communist China. People could track the war's progress daily on a map. They knew exactly who they were fighting, more so when the Chinese entered the fray in late 1950. Combined with the attitude of the day against Communists, as far as the population is concerned, we won the war by securing South Korea's independence.

Fast forward to the Vietnam War and we barely have any of that. The sense of right in our actions was still there, but the flame that drove the hatred in the '50s was starting to sputter and die out. We had ambiguous objectives since it was decided not to invade North Vietnam proper to prevent a repeat of Chinese intervention that occured during the Korean War meaning there was no front line that the population could track on a map. To make it even worse, for the most part of the conflict, just as we see today in the Middle East, it was both hard to track down the opposing force as well as to identify him from friendly South Koreans. As the war dragged on for nearly two decades, the troops on the ground became demoralized, the attitude at home soured, and the politicians realized that supporting the war was political suicide. Men were dying, yet the war was dragging on with, it seemed, no end.

On top of that, the Korean War was overshadowed by the immense fighting of the Second World War and the dragging fight that was the Vietnam War and the hatred that spawned for it. The Korean War was essentially forgotten in the minds of the average American.

Just to add a question of my own regarding the Vietnam war. My dad was a medic during his time in Vietnam and says he feels that it was a politically lost war not a troop lost war. I'm not real up to date on the war in Vietnam and was wondering what you all thought about that statement.

Korea was a just war whereas Vietnam was not. We, meaning the United States, didn't start the fighting in Korea or Indo-China, we just ended up getting drawn in and holding the red hordes at bay and managed to save an entire people, a culture, in the process. to we kind of just had to go wipe the Japanese from the face of the Earth, taking some very difficult territory so undoubtedly we got entangled in the sphere of Asian diplomacy.

There's also the fact that the Red Army was land-grabbing in the area, and Red Chinese troops bolstered the Marxist forces; the Soviet Union provided materiel to those fighting men as a gesture of goodwill or something, who knows

Another very bold point that will hit home: the American invasion force was woefully under-equipped, fought the terrain just as much as the enemy, and the

Edit: Fell asleep

Lost my train of thought. My grandpa was in the 1st marines, at Chosin, and the bloody retreat back. I haven't heard much of his experience, he returned a bitter alcoholic with nightmares and waking flashbacks and once lined up his family in the living room and started brandishing his service pistol at all of them.. You could probably call me biased because I see that personal tragedy overshadowed by the tragedy that was the Korean War. A war fought for freedom: one of the last. My dad's told me that the biggest chip on Gramp's shoulder was that it wasn't declared an actual war in his lifetime..