The classic description of war is "politics by other means." If talking don't work, maybe violence will. For thousands of years, that has been true. People would fight until one side gave up, or was obliterated. Wars of extermination are nothing new. But most wars are much less violent. In fact, most wars have always contained a large component of banditry, mob violence and, in general, what has long been known as "civil disorder."
This changed in the 20th century. Those who control media and public opinion now decide what is a war, and as this process developed during the last century the definition of a war got distorted. What was previously considered banditry or simply civil disorder is now described as a war. A lot of this has to do with how the media is used by the participants in these conflicts. The press release was invented early in the 20th century, and as the decades went by, more and more people realized that a well written press release would be grabbed by the media and turned into news.
The mass media moved information a lot more quickly, so quickly that there was little time for discussion. Popular attitudes could be moved this way or that more easily than ever before. By 1900 it was widely acknowledged that the mass market newspapers were key factors getting America into the 1898 war with Spain. It was downhill from there.
All the American wars of the 20th century were a result, not of U.S. interests, but media generated hysteria. There was no popular desire to get involved in World War I, World War II, Korea, Vietnam or the Gulf War. But attitudes were rapidly changed using the increasingly powerful mass media. This was a big change from how it was done elsewhere. World War I began with kings and emperors determined to avenge real or imagined wrongs. World War II got started because Germany didn't like the way World War I ended. America had no grudges, and no dictator who could just drag us into a war. Each of the America's 20th century wars had a small segment of the population in favor. Most politicians were willing to see which way the wind was blowing before taking a stand. The media also had some owners and editors with pro-war opinions, but mainly, the media looked for the headline that would sell best. Eventually, going to war became the most salable headline and off we went.
Totalitarian nations, which control their mass media, use that power to generate some enthusiasm for the Big Guy's decision to fight. This works, for a while. In democracies, when the people tire of the fighting, the press will switch sides and run with the "get us out of here" angle just as enthusiastically as they did with the "let's fight" headlines. All this headline chasing has one very unfortunate aftereffect. What with all the propagandizing and creative reporting going on, it's very difficult for the historians to come in afterward and figure out what really went on. There job is made more difficult by the flood of "what really happened" books that pour onto the market after the war is over (and a few while the war is going on, if it's a long war.)
Thus in the course of the 20th century, war went from being an extension of politics to an extension of the medias need for eyeball catching headlines. The underlying reasons for the wars were still there, but exactly who gets involved and to what extent is now driven more by how the conflict is pitched in the media. And the modern mass media craves stories that will get more attention. The more scary the better and nothing scares folks as much as the outbreak of war.
What is war anymore? It's a media event. Any kind of civil disorder can be turned into a war by a few enterprising reporters, editors and, most importantly, cameramen. Going into the 21st century, we also have a new force to deal with; NGOs (non-governmental organizations.) The NGOS want support for their good works in strife torn regions, and they have learned that by getting their local problem declared a war by the media makes it easier to force nations to send troops and other assistance.
War isn't what it used to be.