The Flak, or AA, command in an air district is divided into "Groups" known as Flakgruppen. The Groups in turn are divided into "Sub-Groups" called Flakuntergruppen. These types are ordinarily territorial divisions. For example, one of the large industrial cities of Germany is divided into two Groups known as the North and South Groups, and each of these in turn has two Sub-Groups. In addition, there is a Sub-Group for outlying territory east of this town, and one for the northwest approaches.

b. Control Centers

The control center of the Flak defenses is the Group. The Group operates downward through sector controls, which in most cases are the Sub-Groups. These sector controls are the operational headquarters for various purposes—such as, for example, for fire control involving the ordering of barrage fire. The sector control is also used as a communication center. Close liaison is maintained between the Flak organizations and the warning service, and between Flak and air fighter-interception units.

c. Operational Units

Operational units are the battalions, regiments, and higher units. Organization of the individual units above the battalion is not uniform, the exact composition of the unit depending upon the part which it is expected to play in the defense scheme. Thus regiments may be found which consist entirely of searchlight units, entirely of gun units, or even of two mixed gun battalions and one searchlight battalion (the pre-war standard). Even batteries may vary in organization, as in the case of gun batteries where the fire unit is composed of six instead of four guns. Although the battalion (Abteilung) is considered the basic unit, the necessity of deploying batteries makes it impossible in most cases for the battalion commander to exercise detailed control, and the heavy gun battery is normally the fire unit.