America fought two major conflicts in the second half of the 20th century, within the greater Cold War campaign. Both the Korean War and the VietNam War each resulted in over 50,000 US troop deaths and 2.4 million total deaths on both sides. The conventional wisdom in America is that VietNam was a 'failure' and Korea was a stalemate or even a success. However, both assessments may be untrue when viewing the long-term evolution of both theaters through to 2006.
To this day, the US and most of the world worries about North Korea, where a maniacal despot has attained nuclear weapons, and where human development is at African levels. North Korea is a nuclear-armed hypermilitarized prison camp, and a resolution to the current situation may yet prove even more costly than the first Korean War.
VietNam today is a rapidly modernizing nation with a GDP growth rate consistently in the 8% range. While it still is a communist state, it is not belligerent and it does not appear to be at risk of being headed by someone like Kim Jong Il.
The world is extremely fortunate that VietNam, with a population of 85 million, or 4 times that of North Korea, has not become a nuclear-armed state run by a despotic madman, 30 years after the fall of Saigon.
Think, for a moment, about how bad that would be.
In the context of whether the US should have fought either war, it is true that after the end of the Korean War, no further hostilities took place on the Korean Peninsula, whereas after the US withdrew from VietNam, 2 million more people will killed in Cambodia and Laos over the next 5 years. Yet, 31 years later, VietNam is relatively benign, and makes one wonder, in hindsight, whether the same would have happened anyway without US involvement. 53 years after the Korean War, the ripple effects of that are a danger to the world even today, and leads one to think, in hindsight, that the US should have pushed further, sustained more casualties, and unified the entire Korean Peninsula.
One more dimension about the Vietnam War merits consideration - the indirect role it had in turning China away from belligerency. China invaded Vietnam in 1979, possibly lured by the belief that VietNam was greatly depleted at the time. But the Vietnamese had learned many advanced military tactics after 13 years of fighting American forces. China lost 30,000 soldiers in just the first month of their incursion, after which the Chinese army hastily withdrew. Prior to 1979, China had conducted several acts of military aggression, including wars on the Korean Peninsula, the annexation of Tibet, a border war against India (1962), and against the Soviet Union (1969). But after 1979, the PRC has been substantially less willing to conduct expansionist aggression, with no comparable wars occurring since then. Perhaps the Sino-Vietnam War was what induced this change in the PRC's behavior.
Hindsight, of course, is 20/20, and is particularly malleable when given decades of time to look back upon. This is why any judgement on current US involvement in Iraq and Afghanistan will not be settled for quite some time, and those who are quick and eager to brand it a failure reveal a lack of knowledge of historical process (as well as simply fashionable anti-Americanism).
I believe that the US will achieve a distinct victory in Iraq by 2008. I also believe this will force many surrounding nations to change for the better. But the US should learn from the past and not let success in Afghanistan or Iraq lead to an incomplete job at the fringes, and the creation of another North Korea even despite the short term view of success. The plan has to be in the scope of decades, not just months or years.