The Battle of the Bulge (also known as the Ardennes Offensive and the Von Rundstedt Offensive to the Germans) (16 December 1944 - 25 January 1945) was a major German offensive (die Ardennenoffensive), launched toward the end of World War II through the densely forested Ardennes mountain region of Wallonia in Belgium, hence its French name (Bataille des Ardennes), and France and Luxembourg on the Western Front. The Wehrmacht's code name for the offensive was Unternehmen Wacht am Rhein ("Operation Watch on the Rhine"), after the German patriotic hymn Die Wacht am Rhein.
There are several American names for this battle. The first was the description given to the way the Allied front-line bulged inward on wartime news maps, which was reported in the contemporary press as the Battle of the Bulge. The battle was militarily defined as the Ardennes Counteroffensive, which included the German drive and the American effort to contain and later defeat it. Following the war, the U.S. Army issued a campaign citation for its units fighting in northwest Europe at the time. This was called the Ardennes-Alsace campaign and included the Ardennes sector (of the Ardennes Counteroffensive fighting) and units further south in the Alsace sector. The latter units were not involved except for elements sent northward as reinforcements. While Ardennes Counteroffensive is correct military parlance because the official Ardennes-Alsace campaign covers much more than the Ardennes battle region, the most popular description remains simply the Battle of the Bulge.
The German offensive was supported by several subordinate operations known as Unternehmen Bodenplatte, Greif, and Währung. Germany's goal for these operations was to split the British and American Allied line in half, capturing Antwerp and then proceed to encircle and destroy four Allied armies, forcing the Western Allies to negotiate a peace treaty in the Axis Powers' favour. Once accomplished, Hitler could fully concentrate on the eastern theatre of war.
The offensive was planned with the utmost secrecy, minimizing radio traffic and moving troops and equipment under cover of darkness. Although Ultra suggested a possible attack and the Third U.S. Army's intelligence staff predicted a major German offensive, the Allies were still caught by surprise. This was achieved by a combination of Allied overconfidence, preoccupation with their own offensive plans, and poor aerial reconnaissance.
Near-complete surprise against a weakly defended section of the Allied line was achieved during heavy overcast weather, which grounded the Allies' overwhelmingly superior air forces. Fierce resistance, particularly around the key town of Bastogne, and terrain favouring the defenders threw the German timetable behind schedule. Allied reinforcements, including General George S. Patton's Third Army, and improving weather conditions, which permitted air attacks on German forces and supply lines, sealed the failure of the offensive.
In the wake of the defeat, many experienced German units were left severely depleted of men and equipment as survivors retreated to the defenses of the Siegfried Line. For the Americans, with about 610,000 men committed and some 89,000 casualties, including 19,000 killed, the Battle of the Bulge was the largest and bloodiest battle that they fought in World War II.