There are some who call World War II the last 'good war.' I don't know who those people are, nor do I believe that any war can be judged to be 'good.' But I think I understand the comment.
In WWII, the enemy troops wore uniforms, used well-labeled equipment, and held defined positions of geography. There was 'friendly territory' and 'enemy territory.' The war ended when the leaders of the enemy government surrendered, after which their troops laid down their arms and ceased hostility.
Then came the wars in Korea and Vietnam. While the American troops were in uniform, the enemy might be a uniformed soldier, or he might be the teenager who stops by the post every day to mooch a cold soda. The definition of 'friendly territory' became a little more transient as the fighting moved from the battlefield to the village. An American Army or Marine unit could sweep through a village and drive out all the bad guys, but the Americans didn't stay to occupy and defend the village, and the bad guys just moved back in. In fact, the villagers might not have been good guys in the first place.
Or they might be folks who are just trying to survive. While some of the civilians might be fervent followers of whatever revolutionary movement is seeking control, most are just trying to get along without getting killed. The trouble is, it's hard to tell the revolutionaries from those who just want the fighting to stop. American policy has alway been to give the benefit of the doubt to the people, assuming them to be good guys unless they are actually observed trying to do harm. And so, American soldiers and Marines got regularly killed by bad guys hiding in plain sight.
Eventually, our guys get tired of getting picked off this way. After seeing a few of their buddies turned into goo by people they thought they were helping, the fuse finally blows and our guys kill everyone and everything not in an American uniform. And then they get called murderers.
The crime is in putting our troops in this position in the first place. If we can't tell who the enemy is by looking at them, then our troops don't belong there. If the mission isn't to drive invaders from our soil or that of our allies, we shouldn't go. Anything else is a pre-emptive invasion on our part -- and few Americans feel good about being invaders.
WWII wasn't the last 'good war,' if you accept my definition that a 'good war' is one in which our troops can have confidence who is a good guy and who is a bad guy, and that their objective is to get the enemy to surrender by taking away their battlefield positions and destroying their logistics capability.
That distinction goes to Desert Storm -- the operation to kick the Iraqi invaders out of Kuwait. We got to do all the stuff we're good at -- bring all of our technology and organization to bear on a uniformed enemy in defined positions. It was over when the bad guys were driven off our ally's land, and we could declare the mission to truly be accomplished. Admittedly, fighting Iraq isn't like fighting the Soviet Union or China, so it doesn't carry the magnitude of accomplishment of winning WWII. But it was the real deal.
In any war, we ask the young men of our country to point deadly weapons at other human beings and, with little analysis, take the lives of those they have been trained to identify as our enemy. Once they pull the trigger, they will have committed an act that otherwise in our society would been considered one of the worst crimes, punishable by a life in prison or even execution. If we are going to ask them to violate that standard of morality, we need to be sure the identity of the enemy is unambiguous and the mission is just. Otherwise we risk putting them in a situation where they have to quickly evaluate whether the 'civilians' around them are good guys or bad guys, and then act decisively. We doom them to live forever with those decisions.
Iraq is Vietnam all over again. Our mission can't be to drive the invaders out, because the revolutionaries are citizens of that same country. We can't take territory because we are already in the country we're trying to 'free.' Note that I'm not saying that this is a bad thing to do. Helping a country move from dictatorship to democracy is a good thing. But it's not a mission our military forces are built to carry out.
Big wars are won with strategy, tactics, training, leadership and execution. To that you add heroism and a little luck. But it also takes massive manufacturing and logistics capability. To fight a sustained battle, and to win a war, an army needs a constant and massive supply of weapons, ammunition, food and medical supplies. We're pretty good at that, and it's one of the reasons we did so well in Desert Storm.
But when the winning move for the revolutionaries is simply to get the outside power to tire of the pain and leave, you don't need to have, or even want to have, big engagements on the battlefield. This is how the American revolutionaries drove the British from the American colonies. Think about the American Revolution from the perspective of the British sometime. The first battle of the American Revolution took place because the British sent a company of soldiers from Boston to Concord to destroy a weapons cache (I suppose it was the 18th century version of the search for WMDs). The colonists drove the British out of Concord not by lining up and fighting in the civilized manner, but rather by picking them off from the woods. There were a couple of big battles in the Revolutionary War, but we never really defeated the British -- we just made it more painful (and expensive) than they cared to endure. After all, the outcome of the American Revolution was not to have the Americans gain control of the British Isles. We just got them to leave here.
Taking sides in a civil war, or a revolutionary war, is not something we Americans have the stomach to do. Our own Civil War remains the bloodiest conflict we ever engaged in. That's just the way civil wars go -- fighting between brothers always gets nasty. If you want to take sides and win in a civil war, you have to be willing to fight nasty, and we don't like our soldiers and Marines to do that.
It's immoral to send our troops to fight in a nasty war but not let them fight nasty. Let's bring them home before we destroy the minds and attitudes of another generation of our young people.