The Battle of Aachen was a combat action of World War II, fought by American and German forces in and around Aachen, Germany, between 2–21 October 1944. The city had been incorporated into the Siegfried Line, the main defensive network on Germany's western border; the Allies had hoped to capture it quickly and advance into the industrialized Ruhr Basin. Although most of Aachen's civilian population was evacuated before the battle began, much of the city was destroyed and both sides suffered heavy losses. It was one of the largest urban battles fought by U.S. forces in World War II, and the first city on German soil to be captured by the Allies. The battle ended with a German surrender, but their tenacious defense significantly disrupted Allied plans for the advance into Germany.
By September 1944, the Western Allies had reached Germany's western border, which was protected by the extensive Siegfried Line. On 17 September, British, American, and Polish forces launched Operation Market Garden, an ambitious attempt to bypass the Siegfried Line by crossing the Lower Rhine River in the Netherlands. The failure of this operation, and an acute supply problem brought about by the long distances involved in the rapid drive through France, brought an end to the headlong Allied race toward Berlin. German casualties in France had been high – Field Marshal Walter Model estimated that his 74 divisions had the actual strength of just 25 – but the Western Allies' logistical problems gave the Germans a respite, which they used to begin rebuilding their strength. In September, the Wehrmacht high command's reinforcement of the Siegfried Line brought total troop strength up to an estimated 230,000 soldiers, including 100,000 fresh personnel. At the start of the month, the Germans had had about 100 tanks in the West; by the end, they had roughly 500. As men and equipment continued to flow into the Siegfried Line they were able to establish an average defensive depth of .
Supreme Headquarters Allied Expeditionary Force (SHAEF), under the command of General Dwight D.