During the interbellum, the years between World War One and World War Two from 11 November 1918 until September the 1st in 1939 defensive lines were built throughout Europe. The French Maginot Line, the Italian Vallo Alpino, The Stalin Line in the Soviet Union, the Greek Metaxas line, the Rupnik-Line in Yugoslavia and others. The Germans constructed the West Wall, better known in English as the Siegfried line at the borders of the Netherlands, Belgium and France. On the other side of Germany they built the East Wall against a Soviet invasion.
The Oder Warthe bogen at the Ost Wall, looked more like the Maginot line. Bunkers connected by tunnels up to 40 meters deep. But other parts of this East Wall were separate bunkers connected by trenches like the Pommernfestung. Specialized weaponry was developed for these stationary defensive lines. One of them was an automatic mortar installed in a concrete gun position. In the Siegfried wall they used separate bunkers in resistance point of strongpoint setup instead of fortresses and they developed special builds to house the M19 mortar. The Regelbau 633 bunker was developed for his automatic mortar.
The 5 cm M19 Automatic Mortar
The M19 automatic Mortar was developed by Rheinmetall-Borsig from 1934 on and the gun was installed and used from 1938. It fired a 5 cm mortar round of 0,9 kilograms which was also the ammunition for the 5 cm Granatwerfer 36 light mortar used by the German Infantry, and also developed by Rheinmetall Borsig. It reached distances of 50 meters for close defense up to 750 meters. It was a heavy and complex weapon. It weighed 220 kilograms and was operated by at least 4 men. Two men loaded the gun with clips of 6 mortar grenades. One crew member aimed and fired the weapon and one or more crew members reloaded the clips.
It could be used with an automatic firing system or manual. The manual firing of the 5 cm Machinengranatwerfer M19 mortar reached a top of 60 rounds a minute. In automatic mode it reached speeds up to 120 rounds a minute. Which gives the field equivalent of carpet bombing.
436 pieces of this expensive weaponry was ordered but only half of these were produces. The 5 cm Machinengranatwerfer M19 in the photos has serial number 203 and was fabricated in 1940.
Beside the East Wall and West Wall they M19 mortars were used on the Atlantic wall in Regelbau 633 bunkers and in U-boat bunkers.
elow is an example of a Regelbau 633 with an top view on the metal coupola of the 5 cm Machinengranatwerfer M19 mortar (the yellow circle on top). This specific bunker can be found in Stützpunkt Corbière in Channel Island of Jersey.