 Given their view on the state of the German armed forces and their need to push to the Rur, the First Army decided to drive German forces out of the Hürtgen Forest—located on the Belgian–German border—in an attempt to take a series of dams which could be used by the Germans to flood the valley below.The Battle of Hürtgen Forest began on 19 September, with the assault of the 3rd Armored and 9th Infantry Divisions.The battle quickly turned into one of attrition; by mid-October the two Allied divisions had lost nearly 80% of their total combat strength, or roughly 4,500 men, while the Germans had lost close to 3,300.