In the mid-19th century, scholars identified "total war" as a separate class of warfare. In a total war, to an extent inapplicable in less total conflicts, the differentiation between combatants and non-combatants diminishes and sometimes it even vanishes entirely because opposing sides can consider nearly every human resource, even that of non-combatants, to be a part of the war effort.
Actions that may characterize the post-19th century concept of total war include:
The phrase can be traced back to the 1935 publication of the World War I memoir of German General Erich Ludendorff, Der totale Krieg ("The total war"). Some authors extend the concept back as far as classic work of Carl von Clausewitz, On War, as "absoluter Krieg" (absolute war); however, different authors interpret the relevant passages in diverging ways. Total war also describes the French "guerre à outrance" during the Franco-Prussian War.
In his letter to his Chief of Staff, Union General Henry Halleck on 24 December 1864 described that the Union was "not only fighting hostile armies, but a hostile people, and must make old and young, rich and poor, feel the hard hand of war, as well as their organized armies," defending Sherman's March to the Sea, the operation that inflicted widespread destruction of infrastructure in Georgia.
United States Air Force General Curtis LeMay updated the concept for the nuclear age. In 1949, he first proposed that a total war in the nuclear age would consist of delivering the entire nuclear arsenal in a single overwhelming blow, going as far as "killing a nation".