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Command of army group

On 6 June 1944, the Western Allied armies landed in northern France during Operation Overlord. In response, Army Group Upper Rhine (Heeresgruppe Oberrhein) group was formed to engage the advancing US 7th Army (under command of General Alexander Patch) and French 1st Army (led by General Jean de Lattre de Tassigny) in the Alsace region along the west bank of the Rhine. In late 1944, Hitler appointed Himmler commander-in-chief of Army Group Upper Rhine.

On 26 September 1944, Hitler ordered Himmler to create special army units, the Volkssturm ("People's Storm" or "People's Army"). All males aged sixteen to sixty were eligible for conscription into this militia, over the protests of Armaments Minister Albert Speer, who noted that irreplaceable skilled workers were being removed from armaments production. Hitler confidently believed six million men could be raised, and the new units would "initiate a people's war against the invader". These hopes were wildly optimistic. In October 1944, children as young as fourteen were being enlisted. Because of severe shortages in weapons and equipment and lack of training, members of the Volkssturm were poorly prepared for combat, and about 175,000 of them died in the final months of the war.

On 1 January 1945, Hitler and his generals launched Operation North Wind. The goal was to break through the lines of the US 7th Army and French 1st Army to support the southern thrust in the Battle of the Bulge (Ardennes offensive), the final major German offensive of the war. After limited initial gains by the Germans, the Americans halted the offensive. By 25 January, Operation North Wind had officially ended.

On 25 January 1945, despite Himmler's lack of military experience, Hitler appointed him as commander of the hastily formed Army Group Vistula (Heeresgruppe Weichsel) to halt the Soviet Red Army 's Vistula–Oder offensive into Pomerania – a decision that appalled the German General Staff. Himmler established his command centre at Schneidemühl, using his special train, Sonderzug Steiermark, as his headquarters. The train had only one telephone line, inadequate maps, and no signal detachment or radios with which to establish communication and relay military orders. Himmler seldom left the train, only worked about four hours per day, and insisted on a daily massage before commencing work and a lengthy nap after lunch.

General Heinz Guderian talked to Himmler on 9 February and demanded that Operation Solstice, an attack from Pomerania against the northern flank of Marshal Georgy Zhukov 's 1st Belorussian Front, should be in progress by the 16th. Himmler argued that he was not ready to commit himself to a specific date. Given Himmler's lack of qualifications as an army group commander, Guderian convinced himself that Himmler tried to conceal his incompetence. On 13 February Guderian met Hitler and demanded that General Walther Wenck be given a special mandate to command the offensive by Army Group Vistula. Hitler sent Wenck with a "special mandate", but without specifying Wenck's authority. The offensive was launched on 16 February 1945, but soon stuck in rain and mud, facing mine fields and strong antitank defenses. That night Wenck was severely injured in a car accident, but it is doubtful that he could have salvaged the operation, as Guderian later claimed. Himmler ordered the offensive to stop on the 18th by a "directive for regrouping". Hitler officially ended Operation Solstice on 21 February and ordered Himmler to transfer a corps headquarter and three divisions to Army Group Center.

Himmler was unable to devise any viable plans for completion of his military objectives. Under pressure from Hitler over the worsening military situation, Himmler became anxious and unable to give him coherent reports. When the counter-attack failed to stop the Soviet advance, Hitler held Himmler personally liable and accused him of not following orders. Himmler's military command ended on 20 March, when Hitler replaced him with General Gotthard Heinrici as Commander-in-Chief of Army Group Vistula. By this time Himmler, who had been under the care of his doctor since 18 February, had fled to the Hohenlychen Sanatorium. Hitler sent Guderian on a forced medical leave of absence, and he reassigned his post as chief of staff to Hans Krebs on 29 March. Himmler's failure and Hitler's response marked a serious deterioration in the relationship between the two men. By that time, the inner circle of people whom Hitler trusted was rapidly shrinking.