Heeresgruppe A was formed from Heeresgruppe Süd on October 26th, 1939 in the central sector of the Western Front in the Eifel/Hunsrück region. In 1940 it took part in the Western Campaign against France during the Ardennes breakout and the advance to the Somme, and later during operations against Dunkirk. Heeresgruppe A was reorganised during the pause in fighting after Dunkirk. In July it took part in operations in the central sector between the Aisne and Mosel rivers where it advanced to the Swiss borders in the French rear, isolating the Maginot Line.
On October 10th, 1940, Heeresgruppe A was named Oberbefehlshaber West. The commander of the Heeresgruppe (von Rundstedt) became the supreme military commander in the regions Heeresgruppe A occupied. The Heeresgruppe was later disguised as Abschnittstab Winter (also Abschnittstab Silesia/Schlesien) and moved to occupied Poland in the east in preparation for the invasion of the Soviet Union. On June 22nd, 1941 the disguised Heeresgruppe offically became the newly recreated Heeresgruppe Süd.
1939 Nov-Dec 12.Armee, 16.Armee
1940 Jan-May 4.Armee, 12.Armee, 16.Armee (+ 2.Armee)
1940 Jun 2.Armee, 12.Armee, 16.Armee (attached: Panzergruppe Guderian)
1940 Jul 6.Armee, 9.Armee, 16.Armee
1940 Aug 9.Armee, 16.Armee
1940 Sep-Oct 9.Armee, 16.Armee, Commander German Troops in Holland
1940 Nov-Dec 9.Armee, 16.Armee
1941 Jan-Apr 9.Armee, 16.Armee
1941 May 8.Armee, 17.Armee
Gen* Gerd von Rundstedt 10.15.39 - 6.41
* Rundstedt was promoted to Gen.FM on July 19th, 1940.