How is total war different than most wars fought before WW1?
Total war is a conflict in which a nation-state is fully dedicated to a war and focuses all its resources to fighting that conflict.
"Henceforth, until the enemies have been driven from the territory of the republic, the French people are in permanent requisition for army service. The young men shall go to battle; the married men shall forge arms and transport provision; the women shall make tents and clothes, and shall serve in the hospitals; the children shall turn old linen into lint; the old men shall repair to the public places, to stimulate the courage of the warriors and preach the unity of the Republic and hatred of kings."
- Decree for the Levee en Masse, 23 August, 1793.
Total war arose out of the French Revolutionary Wars, when France directed that all of its population, resources and finances be focused on the war effort. In previous conflicts, mobilization to this level was infrequent and usually impossible. Only a modern state with a functioning bureaucracy could achieve it.
Usually, warfare was deemed to be the business of rulers and the military classes, and was also limited by the ability of a government to pay for the upkeep of that military. Civilians could expect to be uninvolved, unless caught in the path of a hostile military who might subject them to robbery, rapine and ruin.
The 19th Century Industrial Revolution made much larger armies and more extensive wars more possible -- railroads in particular could move and supply much larger armies than ever before. The general increase in prosperity allowed Governments to pay for such armies (and Navies). The growth in mass media also made modern propaganda possible.
In the 19th Century, the American Civil War, and the 1870-71 Franco-Prussian War made it clear that for a major war to be waged, almost the whole of society was needed to feed, arm, finance and support a military. Accordingly, the whole of society could then become a target. Sherman's 1864 'March through Georgia' was as much of an example of the new condition as the 1793 French levee in Mass.
WW-1 proved the world's nations understood the new condition.