Steven J. Zaloga - Defense of the Third Reich 1941-45

From 1940 to 1945, Germany was subjected to the most intense aerial bombing campaign to date, totalling some two million tons of bombs. Germanys response to the Allied air attacks was a mix of active and passive air defense tactics, including fighter aircraft, Flak, and air-raid protection. An important but often overlooked aspect of these air defense efforts was an associated fortification program. The Luftwaffes lavishly equipped Flak force is well known, but its methods of deployment and use of field works is detailed here for the first time. The largest single fortification effort inside Germany during the war was a program to create air-raid bunkers and other forms of shelters, an effort four times the size of the Maginot Line construction program. In the final year of the war, Germany attempted to shield its most vital factories from air attack by an urgent scheme to construct underground and fortified factories. Although now forgotten, the Third Reichs air defense fortification program was intensely studied by the Allies after the war and served as the inspiration for many Cold War bunker programs.

The LVZ-West fortification program in the late 1930s in the Saar included numerous command posts such as this LVZ-K bunker, variously designated as a Kommandostand or Gefechtsstand. This bunker was typically used as a Flak battalion command post and was designed to accommodate 24 troops. It was 16m (52ft) wide, 8m (26ft) deep and used 455 cubic metres (600,000 cubic yards) of concrete. (Library of Congress)

The early Flak field works tended to be simple earthen berms around the guns. This is an example of an 88mm Flak G-Stand as displayed in the 1939 Luftwaffe manual for Flak emplacements. (NARA)

Until the mid-1930s, the Flak force had been controlled by the army (Heer) and was primarily oriented towards the tactical defense of the field army. When Hitler renounced the Versailles treaty and created the independent Luftwaffe in March 1935, its new commander, Hermann Gring, took steps to absorb the Flak force into the new Luftwaffe. This was the first step in a process that would eventually see the Luftwaffe assume the primary responsibility for air defense of the Third Reich.

As part of this process, the Luftwaffe embarked on a major rearmament effort that included the acquisition of about 1,900 88mm heavy Flak guns, along with associated gun directors, sound detectors and searchlights. The 88mm heavy Flak gun became the basis for national air defense, supplemented by 20mm and 37mm light Flak guns for low-altitude defense. The air campaigns of the Spanish Civil War in 193639 were intensely studied for lessons regarding the air defense of cities and the value of Flak in modern warfare.

The first major investment in fixed Flak positions for national air defense was part of the larger Westwall fortification effort. By the late 1930s, the principal bomber threat was the French Arme de lAir, and the Westwall program included the Air Defense Zone-West (LVZ-West, or Luftverteidigungszone West). This created a Flak belt stretching from the Eifel region, south through the Saar along the Mosel River, and on to the Black Forest and Swiss frontier. The LVZ-West was not intended to present an impenetrable wall, but rather to act as an initial barrier to French or British bomber attack that would identify the direction of the attack and disrupt it before it could reach its intended target zones deeper in Germany. The initial line consisted of light Flak batteries armed with 20mm and 37mm guns, followed by a second line armed with heavy 88mm guns. Serious construction began in 1938 and was supervised by a special staff of Flak-Regiment 29 in Frankfurt-am-Rhein. In total, 2,056 bunkers were built for LVZ-West from Dren to Karlsruhe through the summer of 1940 at 48 light Flak and 197 heavy Flak sites capable of accommodating 576 light Flak guns and 788 88mm Flak guns. The LVZ-West contained about a third of the heavy Flak batteries available at the start of the war.

The LVZ-West construction was based on seven standard designs. These included command posts (F-Stand, or Fhrerstand, G-Stand, or Gefechtsstand), ammunition bunkers (M-Stand, or Munitionsraum), and personnel shelters (U-Raum, or Doppelgruppenunterstand); V-Stand (Gruppenunterstand am Voderhang), as well as defensive types such as small machine-gun posts. As will be noted, none of the standardized bunkers were designed to accommodate the Flak guns. Instead, the guns were deployed in less expensive earthen fieldworks. The presumption was that the Flak sites were not likely to be primary targets, and that personnel and ammunition were more vulnerable than the guns. Luftwaffe tactical doctrine recognized that there would never be enough Flak guns to cover every possible objective, and so the 88mm heavy Flak gun was designed to be mobile; batteries could be shifted to respond to the objectives of enemy bombing campaigns.

One of the standard configurations for Flak emplacements was the use of a parapet around the G-Stand with outer walls of planks and the space between filled with earth. The ammunition lockers for this 37mm Flak gun were located around the periphery of the gun pit, while one of the lockers was set aside for equipment associated with the gun. This particular emplacement of the 4. Flak-Division was captured by the US 7th Armored Division on the Edersee in the Hesse region in late March 1945. (NARA)

The LVZ-West was the first attempt to create an integrated air defense system incorporating sensors such as searchlights and sound detectors, a common air reporting system, as well as Flak guns and fighter bases. Although the 1937 Luftwaffe armament program included funding for air defense radar, this new technology did not play a major role in the LVZ-West.

At the beginning of the war, the Luftwaffe Flak force was the most lavishly equipped in the world. There were 2,628 heavy Flak guns (88mm and 105mm) compared to about 1,300 heavy anti-aircraft guns in Britain. Although the Luftwaffe was responsible for both strategic air defense of the Reich and tactical air defense of the army, in 1939 about 80 percent of its resources were devoted to homeland defense. The one area where Britain had a significant lead was in its integrated air defense system which included the Chain Home radars and a sophisticated network of forward observers and air reporting centres which collated the data and passed it on to both the fighter and AA gun force. Germany had begun to take steps in this direction, but it had not integrated early warning radars into its network as extensively as in Britain. In late 1939, the Luftwaffe had only eight Freya early warning radars on the German Bight, the small stretch of coastline along the North Sea between the Netherlands and Denmark that was especially vulnerable to British bomber attack.