This U.S. Army map from World War I shows the U.S. and opposing German lines and presumed enemy order of battle in the vicinity of Sommerance, France, on October 7, 1918. German forces are classified by their quality of fighting skill; the best units are ranked as first class and poorest as fourth class. Units are broken down into division and then regiment. The length of time a unit had spent on the front line is noted as such information could help planners determine the combat effectiveness or war weariness of a given unit. Territory seized as a result of an American minor attack on October 6 is shown. The information contained in maps of this kind was derived from a variety of sources, including captured German maps, statements by prisoners of war, and aerial surveillance and photography. The fighting shown was part of the great offensive of September 26–November 11, 1918, the final push along the entire Western front by which the Allies hoped to drive the Germans out of France and thereby win the war. The main American attack was carried out by the First Army under General John J. Pershing in the approximately 35-kilometer wide section of the front between the Meuse River and the Argonne Forest. Three corps, each comprised of three divisions with one in reserve, made the attack. The Fifth Corps was in the center and was expected to strike the decisive blow, flanked by the First Corps on the left and the Fourth Corps on the right. To carry out the operation, 600,000 American troops had to replace 220,000 exhausted and battle-weary French troops prior to the attack. The scale of this map is 1:20,000. The map is from the collection of U.S. Army Major General Charles P. Summerall, commander of the Fifth Corps.