21 cm Mörser 18
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| 21 cm Mörser 18 | |
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| Name | 21 cm Mörser 18 |
| Origin | Germany |
| Type | Siege mortar |
| Service | 1939–1945 |
| Used by | Wehrmacht, Waffen-SS |
| Wars | World War II |
| Designer | Rheinmetall |
| Design date | 1933–1938 |
| Manufacturer | Rheinmetall-Borsig |
| Production date | 1938–1943 |
| Number | ~1,100 |
| Weight | 16,700 kg (combat) |
| Length | 5.1 m (barrel) |
| Cartridge | Separate-loading, cased charge |
| Caliber | 210 mm |
| Rate | 1 round per 2–3 minutes |
| Velocity | 570 m/s (max) |
| Range | 16,725 m (max) |
| Breech | Horizontal sliding-block |
| Recoil | Hydro-pneumatic |
| Carriage | Box trail, firing platform |
| Elevation | -6° to +70° |
| Traverse | 6° |
21 cm Mörser 18 The 21 cm Mörser 18 was a German heavy siege mortar fielded by the Wehrmacht and Waffen-SS during World War II. Designed and produced by Rheinmetall and Rheinmetall-Borsig in the late 1930s, it combined heavy high-explosive firepower with relatively mobile carriage features derived from earlier German siege artillery. The weapon saw service in major campaigns including the invasions of Poland (1939), France, and the Eastern Front operations against the Soviet Union.
Design and Development
Rheinmetall developed the 21 cm Mörser 18 as a successor to the World War I-era 21 cm Mörser 16 to meet requirements set by the Reichswehr and later the Heer for a heavy mortar capable of counter-battery and siege roles. Drawing on engineering concepts used by Krupp and lessons from the Interwar period, designers implemented a split-trail-like box carriage and a hydro-pneumatic recoil system similar to contemporary designs such as the 15 cm sFH 18 and the 10.5 cm leFH 18. Prototype trials at the Kummersdorf proving grounds and evaluations by the Heereswaffenamt refined elevation mechanisms and transportability using six-axle trailers often towed by Sd.Kfz.7 half-tracks or heavy prime movers used by Panzerarmee logistics units.
Technical Specifications
The mortar featured a 21 cm caliber, 5.1 m tube with a horizontal sliding-block breech, and separate-loading ammunition with cased charges managed by crews from Artillerie-Regiment establishments. The hydro-pneumatic recoil allowed firing at elevations up to +70° and a limited traverse of about 6° on the firing platform, enabling employment in both direct and steep-trajectory bombardment roles favored in sieges like Siege of Sevastopol (1941–42). The combat weight of approximately 16,700 kg required assembly time comparable to other heavy artillery such as the 8.8 cm Flak 18/36/37 when emplaced. Sighting equipment and fire-control inputs were provided in coordination with Artillerie- Regiments using range tables and forward observers from units like Heeres-Pioniertruppe.
Operational Use and Service History
Deployed from the outbreak of World War II, the Mörser 18 equipped heavy batteries within German corps-level artillery organization and fortress detachments defending locations such as Atlantic Wall strongpoints and Festung Königsberg. It participated in the Battle of France for fortress reduction and in the Siege of Leningrad and Siege of Sevastopol (1941–42) where its high-angle fire was used against fortifications and bunkers. On the Eastern Front, logistic strain and terrain often limited the mortar's mobility during offensives like Operation Barbarossa, but it remained valuable in static siege conditions and defensive battles near Stalingrad and Kursk. Post-1943 production declines and the emphasis on self-propelled artillery reduced new Mörser 18 allocations, though several remained in service with units attached to Heeresgruppe Süd and Heeresgruppe Mitte through 1945.
Ammunition and Firing Performance
Ammunition types included heavy high-explosive (HE) shells, concrete-piercing rounds for fortification reduction, and specialized charges developed during collaboration between Rheinmetall and the Heereswaffenamt. Typical projectile weight was in excess of 100 kg with muzzle velocities reaching about 570 m/s depending on charge, delivering maximum ranges near 16,725 m with full charges. Accurate fire depended on forward observers from formations such as Aufklärungs-Abteilung and coordination with meteorological data similar to procedures used by Artillerie-Schule units. Rate of fire was limited by loading complexity to roughly one round every 2–3 minutes in sustained action, though shorter bursts were possible during intensive bombardment.
Variants and Modifications
Variants included field modifications for improved transport and limited experimental mountings on railway platforms inspired by earlier conversions like the Eisenbahngeschütz family and contemporary practices seen with K5 (E) railway gun adaptations. Some Mörser 18 pieces received reinforced recoil anchors and modified firing platforms for coastal defense emplacements along the Atlantic Wall and in Norway where cold-weather kits and corrosion-resistant coatings were trialed. Late-war improvisations by units such as Festungartillerie incorporated captured prime movers or static emplacements to maintain operational availability after losses of towing vehicles.
Combat Evaluation and Effectiveness
In combat, the 21 cm Mörser 18 was judged effective against fortifications, bunkers, and reverse-slope positions, earning praise from staff officers in after-action reports from the Siege of Sevastopol (1941–42) and the Battle of France. However, its heavy weight and limited traverse constrained tactical mobility compared with more versatile systems like the 15 cm sFH 18 and growing numbers of self-propelled guns such as the Hummel (vehicle). Logistical demands, including transport and ammunition supply lines overseen by Nachschubtruppe, limited its deployment in fast-paced campaigns exemplified by Operation Barbarossa. Despite these limitations, the Mörser 18 remained a valuable asset for fortress reduction and static defense through the end of World War II.
Category:Artillery of Germany 1939–1945