Army Group B was initially created on 12 October 1939, when the former Army Group North, which had participated in the Invasion of Poland, was renamed. The initial commander of the army group was Fedor von Bock,^[1]: 22 who had already held the command over Army Group North during the campaign in Poland.^[1]: 166

Army Group B was assembled during the period of the Phoney War in the Lower Rhine area, along the German-Dutch border and the German-Belgian border.^[1]: 22 In the initial OKH draft for the attack against France, Army Group B was assigned the Schwerpunkt role, but the intervention by senior officers (notably Erich von Manstein) from its southern neighbor, Army Group A, resulted in a shift in the German planning starting in January to February 1940.^{[2]: 78–81} Army Group A was now accorded the operational focus, and Army Group B became a formation with a support and auxiliary role. With 29⅓ divisions, it was clearly smaller than its southern neighbor with 44⅓ divisions (whereas Army Group C in the far south on the French border received only 17 divisions).^[3]: 254 Army Group A also received preferential treatment in terms of access to reserve formations.^[2]: 105 Whereas Army Group A received seven armored divisions and three motorized infantry divisions, Army Group B was significantly weaker at three each.^[4]: 312

The army group participated in the German invasion of the Netherlands and the German invasion of Belgium. In the second part of that campaign ("Case Red"), Army Group B again found itself on the right-hand flank of the German forces and advanced towards the Somme river and to the French Atlantic coast.^[1]: 22

After the successful conclusion of the Western campaign, the army group initially remained on occupation duty in German-occupied France, but was redeployed to German-occupied Poland starting on 16 August 1940, where it took charge of German forces in East Prussia and the General Government, in proximity to the demarcation line with the Soviet Union.^[1]: 22

On the day Germany invaded the Soviet Union ("Operation Barbarossa"), 22 June 1941, Army Group B was renamed "Army Group Center".^[1]: 22

On 9 July 1942, the previous Army Group South was split in two, resulting in the creation of a new Army Group A as well as the creation of a new Army Group B. Whereas Army Group A was led by a new army group command that had been covertly prepared behind the lines (as "Staff Anton"),^[1]: 8 Army Group B remained in charge of the previous Army Group South's command formation.^[1]: 216

Army Group B advanced northeastwards (whereas Army Group A moved south into the Battle of the Caucasus) to approach the Don and Volga rivers, with particular goals at the Soviet cities of Stalingrad and Astrakhan. After the forward formations of the army group got themselves entangled in the Battle of Stalingrad, a Soviet counterthrust ("Operation Uranus") left the German 6th Army encircled inside the city, on the Volga west bank. Several major formations (German 6th Army, Romanian 4th Army, German 4th Panzer Army) were transferred away from Army Group B and attached to the newly-formed Army Group Don in November 1942. After another Soviet breakthrough on the Don river on 14 January 1943 (Voronezh–Kharkov offensive), Army Group B was pulled out of the line on 9 February 1943. Its remnant subordinate formations were distributed either to the Army Group Center or to the new Army Group South (previously Army Group Don).^[1]: 23

After Army Group B was pulled out of the Eastern Front, its remaining staff elements were combined on 19 July 1943 with another staff, Task Force Rommel (German: Arbeitsstab Rommel), named after its leading officer Erwin Rommel (whose Army Group Afrika had recently been decisively defeated with the ends of the Tunisian campaign). Rommel on the same 19 July became the commander of Army Group B.^[1]: 23

The army group was deployed to northern Italy, where much of its staff was restructured into Army Group C ("Supreme Commander South West") on 26 November 1943.^[1]: 23

On the same day that the staff of Army Group B was dissolved in Italy (26 November 1943), an army group high command by the same name was created in German-occupied France.^[1]: 23

After the Western Allies' Normandy landings (6 June 1944), Army Group B became the northern army group in the German line on the Western Front. Günther von Kluge assumed command of the army group on 19 July 1944, but was soon replaced by Walter Model on 17 August.^[1]: 23 Moving to the Low Countries, Model with his HQ located at Oosterbeek close to Arnhem, was surprised on 17 September by the start of Operation Market Garden. The army group also participated in the Battle of the Bulge.^[5]: 106

Army Group B was isolated in the Ruhr Pocket in northern Germany, and after being divided up into smaller and smaller sections, the final section surrendered to the Allies on 21 April 1945. Model committed suicide the same day.^[6]

Commanders

• Generalfeldmarschall Fedor von Bock (3 October 1939 – 1 April 1941)
• Generalfeldmarschall Maximilian von Weichs (15 July 1942 – 10 July 1943)
• Generalfeldmarschall Erwin Rommel (10 July 1943 – 17 July 1944)
• Generalfeldmarschall Günther von Kluge (17 July 1944 – 15 August 1944)
• SS-Oberst-Gruppenführer Paul Hausser (15 August 1944 – 17 August 1944)
• Generalfeldmarschall Walter Model (17 August 1944 – 17 April 1945)

Chief of Staff

• General der Infanterie Hans von Salmuth (3 October 1939 – 1 April 1941)
• General der Infanterie Georg von Sodenstern (15 July 1942 – 19 July 1943)
• Generalleutnant Alfred Gause (19 July 1943 – 15 April 1944)
• Generalleutnant Hans Speidel ( 15 April 1944 – 1 September 1944)
• General der Infanterie Hans Krebs (1 September 1944 – 17 February 1945)
• Generalmajor Carl Wagener (20 February 1945 – 17 April 1945)