How did WWI change the way war was fought? How did it change the world? And how did it change the way people viewed war?

World War I changed the way wars were fought because of the widely known trench warfare. Since troops in trenches were much more protected than their fellow troops that were outside, it lengthened battles. It changed people's views, because people saw it as the war to end all wars, so it probably made some people think wars would be more rare, or just non-existent.