The Battle of Hürtgen Forest (German: Schlacht im Hürtgenwald) is the name given to the series of fierce battles fought between U.S. and German forces during World War II in the Hürtgen Forest, which became the longest battle on German ground during World War II, and the longest single battle the U.S. Army has ever fought. The battles took place from 19 September to 16 December 1944, over barely 50 sq mi (130 km2), east of the Belgian–German border. The U.S. commanders' initial goal was to pin down German forces in the area to keep them from reinforcing the front lines further north in the Battle of Aachen, where the Allies were fighting a trench war between a network of fortified towns and villages connected with field fortifications, tank traps and minefields.
A secondary objective may have been to outflank the front line. The Americans' initial objectives were to take Schmidt and clear Monschau. In a second phase the Allies wanted to advance to the Rur River as part of Operation Queen. Generalfeldmarshall Walter Model intended to bring the Allied thrust to a standstill.
While he interfered less in the day-to-day movements of units than at Arnhem, he still kept himself fully informed on the situation, slowing the Allies' progress, inflicting heavy casualties and taking full advantage of the fortifications the Germans called the Westwall, better known to the Allies as the Siegfried Line. A few days later, the Battle of the Bulge began, leaving the battle of Hürtgen Forest largely forgotten.
The Hürtgen Forest cost the U.S. First Army at least 33,000 killed and incapacitated, including both combat and noncombat losses; German casualties were 28,000. Aachen eventually fell on 22 October, again at high cost to the U.S. Ninth Army. The Ninth Army's push to the Rur fared no better, and did not manage to cross the river or wrest control of its dams from the Germans. The Rur triangle was later cleared during Operation Blackcock between 14 and 26 January 1945.
Hürtgen was so costly that it has been called an Allied "defeat of the first magnitude", with specific credit being assigned to Model.
The Germans fiercely defended the area for two reasons: it served as a staging area for the Ardennes Offensive (what became the Battle of the Bulge) that was already in preparation, and the mountains commanded access to the Schwammenauel Dam at the head of the Rur Lake (Rurstausee) which, if opened, would flood low-lying areas downstream and deny any crossing of the river. The Allies only recognized this after several heavy setbacks, and the Germans were able to hold the region until they launched their last-ditch offensive on the Western Front into the Ardennes.