42 cm Gamma Mörser
The 42cm kurze Marinekanone L/12, or Gamma-Gerät, was a German siege gun built by Krupp. The Gamma-Geräts barrel diameter was, making it one of the largest artillery pieces ever fielded. It was designed from 1906 to 1910, then used by the Imperial German Army during World War I at various sieges and battles in Belgium, France, Poland, and Serbia. A single Gamma-Gerät survived World War I and saw limited use in World War II by the Wehrmacht to attack the Maginot Line and besiege Sevastopol.
Due to its extreme weight, 150 metric tons, it was mostly immobile and had limited effectiveness on either the Western and Eastern Fronts of World War I. Only ten were built.
Development
The quick advancement of artillery technology beginning in the 1850s provoked rapid advancements in artillery and military architecture. When rifled artillery became able to fire out of range of fortress guns, military architects began placing forts in rings around cities or in barriers to block approaching armies. New high-explosive artillery shells, which could penetrate earth to destroy masonry underground, made these forts themselves vulnerable to artillery. In response, star forts evolved into polygonal forts, placed mostly underground and made of concrete with guns mounted in armoured, rotating casemates. Combining rings and barriers, France created a vast fortified zone on their border with Germany. Meanwhile, Belgium began construction of the National Redoubt in 1888.The German Empire also fortified its borders, but Chief of the General Staff Helmuth von Moltke the Elder desired to break through Franco-Belgian fortifications. Although German artillery had been effective during the Franco-Prussian War, by the 1880s the diameter of the German Army's most powerful gun,, had become the standard thickness for fortress concrete. Moltke began requesting more powerful guns that same decade, which then became essential to his successor, Alfred von Schlieffen, who planned to quickly defeat France by sweeping through Belgium in response to the 1893 Franco-Russian Alliance. That same year, the German Army's formed a secret partnership with Krupp to supervise development of a weapon that could break Franco-Belgian fortresses. Acting on a study that showed that a shell could penetrate modern fortresses, Krupp designed and built a 30.5cm mortar, the Beta-Gerät. The Beta-Gerät was adopted into service in 1897 as the schwere Küstenmörser L/8, a cover name concealing its true purpose, making it Germany's first large artillery piece to have a breech and a recoil system. Further studies conducted by the APK in the mid-1890s showed that the Beta-Gerät could not penetrate the armor of modern Franco-Belgian forts, even with revised shells. Interest in an improved siege gun waned until the Russo-Japanese War, during which the Japanese Army used coastal mortars brought from Japan to end the 11-month long Siege of Port Arthur.
Helmuth von Moltke the Younger, Chief of the General Staff since 1 January 1906, saw the utility of a newer, larger siege gun. In 1906, he instructed the APK to conduct further evaluation of the Beta-Gerät. The resulting study suggested a siege gun with a caliber as large as, but the German Army opted for a 30.5cm howitzer and a 42cm gun. The howitzer, the Beta-Gerät 09, had a greater range and accuracy than the Beta-Gerät, but was difficult to transport and could not penetrate fortress concrete. Only two were produced. Meanwhile, the 42cm gun was designed in 1906 and its first model was delivered for testing in May 1909. After initial difficulties with penetration, the gun was accepted into the German Army in 1910 as the kurze Marinekanone L/12, or the Gamma-Gerät. The first in-service Gamma-Gerät was ordered in 1910, followed by another in 1911, three more in 1912, and an additional five during World War I. In total, ten were manufactured, along with 18 additional barrels. The power but near-immobility of the Gamma-Gerät inspired further development by the APK, who addressed mobility in the development of the M-Gerät "Big Bertha" howitzer by pulling it with tractors.
Design and production
With a maximum range of and a high degree of accuracy, the Gamma-Gerät was the Imperial German Army's most powerful siege gun. The Gamma-Gerät was essentially an enlarged Beta-Gerät 09 weighing, ensuring that it could only be emplaced near permanent railways in a process that took 24 hours. To emplace the Gamma-Gerät, all nearby vegetation was cleared and a rectangular pit was dug and then reinforced with timber and steel to form the bedding. At the same time, a rail spur was spun off the nearest permanent line to the site. Then, a rail-mounted gantry crane was unloaded and used to assemble all seven, portions of the Gamma-Gerät. Fully assembled, the gun stood high and long. Its standard rate of fire was one shell every seven minutes and eight shells in an hour. The fastest recorded rates of fire were 19 shells an hour for a single Gamma-Gerät and 30 shells an hour for a two-gun battery. The gun had an elevation of 43° to 66°.| Name | Calibre | Weight | Range | Rate of fire | Time to emplace |
| M-Gerät "Big Bertha" | 8 shells an hour | 5–6 | |||
| Gamma-Gerät | 8 shells an hour | 24 | |||
| Beta-M-Gerät | 8 shells an hour | 7–8 | |||
| Beta-Gerät 09 | 12 shells an hour | 12 | |||
| Beta-Gerät | 15 shells an hour | 12 |
Ammunition
German siege artillery had three types of projectiles: armour-piercing, high-explosive, and intermediate. The armour-piercing shell was designed to smash through concrete and metal armour, but was largely ineffective against reinforced concrete. High-explosive shells were fitted with two charges and could be set to have no delay, a short delay, or a long delay. If set to "no delay," then the shell burst on impact. 42cm high-explosive shell craters could be as wide as and as deep as. If set to a delayed detonation, it could penetrate up to of earth. Finally, the intermediate, or "short shell," weighed half as much as the high-explosive shell and was fitted with a ballistic tip for range and accuracy. 42cm shells were generally long, weighed between, and were propelled via primer loaded into the gun with a brass casing. Siege artillery shells were produced in limited runs of varying quality. Beginning in early 1916, German siege guns began to suffer internal explosions due to faulty ammunition. As a result, crews were required to disembark from the gun before firing via a lanyard.Service history
The kurze Marinekanone Batteries that formed with Gamma-Gerät guns were 1, 2, and 4. In April 1916, Batteries 1 and 2 were split to form additional batteries: 8, 9, and 11. When Battery 8 had its guns destroyed by internal explosion in 1917, it was outfitted with two Beta-M-Gerät mortars, converted from the destroyed Gamma-Gerät guns.World War I
With the start of World War I, all siege-gun batteries were mobilised and assigned to the Western Front. KMK Battery 2 was sent north to Namur, but could not arrive in time to participate in the Siege of Namur, while KMK Battery 1 was assigned to the 6th Army in Lorraine. As part of the 6th Army, it participated in the siege of the from 25–27 August 1914. During the 52-hour siege the battery had technical troubles and had to stop firing. KMK Battery 1 finally arrived at the then-ongoing siege of Maubeuge in early September and joined the siege guns already present in obliterating Forts Leveau, Héronfontaine, Cerfontaine, and Sarts. On 7 September 1914, with only two forts remaining in French hands, Maubeuge's garrison surrendered.The German defeat at the First Battle of the Marne prevented the siege guns at Maubeuge from being sent against Paris, so they were sent back into Belgium to Antwerp. The Belgian Army, which had retreated to the city on 20 August following the fall of Liège, had made attacks on the German flank on 24–25 August and 9 September. In response, the III Reserve Corps, from the 1st Army, was sent to capture the city. The Corps arrived at Antwerp on 27 September, partially surrounding it and massing at its southern side. The next day, KMK Battery 2 opened bombardment against the Fort de Wavre-Sainte-Catherine, which was destroyed on 29 September by a magazine detonation caused by a 42cm shell. KMK Battery 2 then shifted its fire to the, which surrendered on 2 October. Beginning on 7 October and lasting the next two days, Antwerp's defenders began withdrawing from the city, which then surrendered on 10 October. With the fall of Antwerp, KMK Battery 2 was attached to the 4th Army to aid in its capture of the Channel ports, and occasionally shelled Nieuport, Ypres, and Diksmuide.
On 27 February 1915, KMK Battery 1, with the 8th Army, joined the ongoing attack on Osowiec Fortress. Although the fortress was made of masonry, it survived, intact, because the artillery had no spotters to guide its fire and because of effective counter-battery fire from the fortress. After five days, the siege guns were withdrawn and the fort was besieged until August. On 8 August, KMK Batteries 1 and 4 fired on Kaunas Fortress to support the XXXX Reserve Corps. While slow, the bombardment was highly effective because of outdated masonry construction, and the Germans took four forts altogether on 16–17 August. The Russians evacuated from the city and fortress the next day. The last action for Gamma-Geräts in the East was the German Invasion of Serbia. On 6 October 1915, KMK Batteries 1 and 4 opened fire on Serbian fortifications east of Belgrade to support the crossing of the 11th Army, made the next day. Battery 1 briefly fired on Smederevo Fortress, but the fortress was undamaged when it surrendered on 11 October.
KMK Batteries 1 and 4 were transferred back to the Western Front in early 1916. The latter bombed Forts Douaumont and Vaux without effect while the former inflicted serious damage on a French railway viaduct east of Belfort. At the beginning of that year, all 42cm guns were assigned to the 5th Army for the upcoming Battle of Verdun. The battle began on 21 February with an intense, nine-hour artillery barrage. The 42cm guns were tasked with bombarding Forts Douaumont, Vaux,, and, the most modern fortresses at Verdun, to silence their guns and prevent French units from rallying at them. However, despite heavy shelling by all thirteen 42cm guns, the forts were only lightly damaged. At the same time, French counter-battery artillery and internal explosions plagued German siege guns; KMK Batteries 2, 8, and 9 lost a Gamma-Gerät each. In July, siege batteries began to be withdrawn north to the Battle of the Somme, and east to Romania. KMK Battery 4 remained at Verdun, while Battery 1 attacked Arras and Loos-en-Gohelle in June and July.
In the last two years of the war, siege guns saw limited use and negligible effect on the Western and Eastern fronts. For the Spring Offensive, KMK Battery 4 was assigned to the 17th Army on the Somme. When the time for Germany's final offensive operation came in July, the gun was assigned to the 1st Army at Reims but had accomplished little in the battle. KMK Battery 4 survived the reorganization of the German Army in late 1918, but with a single gun.