The Order of Battle for the Wehrmacht on May 10, 1940, shows the German force involved being divided into three major organizational blocks. Each one of these “blocks” is referred to as Heeresgruppe – or army group. Consequently, they are named Heeresgruppe A, Heeresgruppe B, and Heeresgruppe C.
Oberkommando des Heeres (OKH)
At the highest level, the Oberkommando des Heeres (OKH) is represented by Generalfeldmarschall Walter von Brauchitsch.
Heeresgruppe A was under the command of Generaloberst Gerd von Rundstedt. Their responsibility was the swift attack through the Ardennes.
Heeresgruppe B was under the command of Generaloberst Fedor von Bock. This group was taking the responsibilities to attack Belgium and the Netherlands.
Heeresgruppe C was under the command of Generaloberst Wilhelm Ritter von Leeb. This group was placed on the southern part of the western front and was to take the responsibility for the break-through of the Maginot Line.