The bloody nature of the American Civil War almost cost Lincoln re-election in 1864. Had the "peace at any price" party won, the south would have won. Lincoln prevailed in the election only because of some last minute victories by his armies. The war ended 18 months after Lincoln's re-election, more of a near run thing than most people like to remember.
The civil war was the bloodiest in the nations history, with 558,000 dead. This had an enormous impact on American attitudes towards war. Remember that 14.4 percent of the 3.8 million men who served in the war died. The only subsequent war to even come close was World War I and World War II (2.5 percent each.) Korea (.6 percent) and Vietnam (.7 percent.) A better way to understand how these wartime deaths hit home was to consider the war dead per thousand population. In the civil war, it was 16 per thousand population. That means nearly everyone had a family member or neighbor who died. In World War II it was three per thousand and Vietnam was a tenth that rate.
Half a million American lives wasn't the only thing we lost in the civil war. Any illusions about military glory went as well. While presidents and congressmen may have thought it a good idea for America to get involved in wars over the last 150 years, they always had to deal with tremendous resistance from the American people. It always took some bloody attack on Americans to get the population suitably inflamed to go along. In the Spanish American War it was the American battleship "Maine" blowing up in a Spanish port. In World War I there were Americans getting killed by German submarines, in World War II it was Pearl Harbor, Korea was naked North Korean aggression (which Iraq provided in the Gulf War.) Vietnam required an invented (as was revealed later) attack on the U.S. fleet in the Gulf of Tonkin.
The desire for revenge, or fear of further attacks, got the American people in a warlike mood. But only for a while. U.S. politicians with any sense of history know that this enthusiasm has a very short shelf life. Abraham Lincoln learned this the hard way. So did Harry Truman, coming into office unexpectedly when president Roosevelt died, and had to deal with getting World War II over with before public opinion made him extremely unpopular. Dwight Eisenhower and Richard Nixon got elected by promising to end the Korean and Vietnam wars, respectively. George Bush stopped the Gulf War ground offensive at 100 hours partly to avoid battle fatigue among the voters.
Even a popular conflict like World War II was handled carefully by the government. No photos of dead American soldiers were allowed to be shown until 1943, and journalists were given a lot of guidance on how the war should be presented to the American people. Even so, by 1945, war weariness was growing. The dropping of the atomic bombs on Japan received near universal acclaim from the American public. Those bombs stopped the fighting, which was particularly brutal in the Pacific and "brought the boys home." Victory was enthusiastically savored, but the cost was not forgotten.
Both Korea and Vietnam were brought to an end short of victory because the population was tired of the losses. The Cold War that replaced World War II was not a bloodless conflict. Over a hundred thousand Americans died fighting the Cold War, mostly in Korea and Vietnam. Since the Cold War did not open with something dramatic like Pearl Harbor, losses were less tolerable. Korea left Americans in an ugly mood, and the government had to lie (OK, it was mainly over optimism) big time to get voters to go along with Vietnam. Out of that experience came the popular expression, "no more Vietnams."
Unfortunately, America gets into most of its wars because the political leadership, not the voters, think it's a good thing. In the post Cold War world, there are many overseas situations that cry out for justice in the form of American military power. But presidents need to convince the voters, or at least congress, that sending in the troops is a good idea. While Pearl Harbor was not staged by Roosevelt to get us into World War II, many Americans remain convinced that it was. Since then we have the sad revelation that the Gulf of Tonkin incident was basically made up to enable president Johnson congressional permission to send troops into Vietnam. President Clinton lied about American troops only being in Bosnia for a year.
These two American traditions, popular distaste for war, and presidents willing to lie to get us into them, are not likely to disappear any time soon.
A Long American Tradition- How unwilling are Americans to lose their sons and daughters in combat? A lot, and this has been the case for a long time. We tend to forget this unique aspect of American history. During the American Revolution, general Washington generally avoided battles and American casualties in general. Many Americans were not really enthusiastic about the revolution, and too many rebel dead could make many Americans think that perhaps king George wasn't such a bad fellow after all.