The First Army Group guarded the north-east frontier of France, ready to move into Belgium and the Netherlands to oppose any German invasion of those nations.
The Belgian Army field approximately 600,000 personnel in 22 divisions, backed by 1,338 artillery pieces, 10 tanks and 240 other combat vehicles.
King Leopold III of Belgium had assumed personal command of the army upon mobilization.
His principal military advisor was Lieutenant-general Raoul Van Overstraeten, while General-major Oscar Michiels was Chief of the General Staff.
The following divisions were also kept in reserve: The commander-in-chief of the Oberkommando des Heeres (OKH) was Generaloberst Walter von Brauchitsch.