Kazemat (B10), Bloklaan bij 9

English translation

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Description

Cluster 16. Cast steel dome casemates type G.

NEW HOLLANDIC WATERLINE

Introduction

CAST STEEL DOME CASEMATES TYPE G as components added during the Interbellum period to linear and access defence, with trench systems, group shelters and similar, of which at least two specimens remain. The specimens near Fort Spion served to defend the access of the Bloklaan, but during the occupation they were stripped of the cast steel dome; only concrete blocks in which these domes were mounted remain. In 1936, as a supplement to the reinforced concrete casemate, the so-called cast steel dome casemate was introduced in the Netherlands, which was based on a system already applied in France in 1917. The armoured domes used were small in size (favourable regarding visibility and hit probability), round in shape (favourable regarding strength and deflecting hits), relatively simple to produce in series and they had an 'external' firing opening (favourable regarding gases and sound). Moreover, they could be manufactured in the Netherlands, which significantly reduced dependence on foreign countries. A first order of 100 pieces in the Netherlands (at DEMKA) was followed by a second of 50 pieces from the Belgian Société Anonyme John Cockerill. In total, over 700 must have been cast in a short time, but only a few of these have survived. The cast steel domes, with a diameter of 1.75 m and thicknesses of 10-14 centimetres, are installed in multiple casemate types with resistance classes W 12-15 and W 21-28. Most domes were placed in Standard Dome Casemates Type G. Shortly before the start of the Second World War, so-called Dome Casemates Type G were constructed at various places in the Dutch lines, in particular in the IJssel line, the Maas line, the Grebbe line (each approximately 150) and the New Hollandic Waterline (approximately 80, in a reinforced version of 14 centimetres thickness). The usual construction of reinforced concrete with one or more fixed firing ports was abandoned in favour of a system that possessed a firing direction projectible within variable limits (up to 270°), within a cast steel cylinder with dome roof. Standard Dome Casemates in the NHW were equipped with a heavy machine gun as armament. Standard dome casemates were applied among others to defend 'new or improved accesses', that is to say at places where new (motor)roads or electrification of railways were planned or realised. The front side could be provided with an earth covering and camouflage. Dome casemates type G were usually approachable and accessible via trenches; in the vicinity were usually group shelters type P. During the Second World War, the vast majority of domes in the interior were dismantled by the occupier from the casemates - partly by blowing them up - with the aim of recasting them for other steel requirements. On the coast, they were partly incorporated into the defence, but were often demolished after the war nonetheless. As a result, complete dome casemates are rare; they can in any case still be found at the Fort at Vechten and there is also a specimen at the Fort at Rijnauwen. The concrete constructions in which they were placed occur more frequently - but mostly in damaged form. The specimens near Fort Spion have also been dismantled; one of them lies in a wooded environment, while another specimen is in the open field.

Description

CAST STEEL DOME CASEMATES TYPE G of a type of which specimens were built at various places in the Dutch lines shortly before the start of the Second World War. The usual construction of reinforced concrete with one or more fixed gun ports was abandoned in favour of a system that possessed a firing direction projectible within variable limits (up to 270°), within a cast steel cylinder with dome roof. Cast Steel Dome Casemates could among others be equipped with a heavy machine gun as armament. Standard cast steel dome casemates type G are relatively low, virtually square, concrete casemates (approx. 7.00 x 6.50 x 2.20 m; w x d x h), with a rearward-sloping surface at the height of the dome recessed therein. The firing opening in the dome formed a rounded rectangular 'eyebrow' of approximately 10 cm thickness, which protruded some decimetres outside the dome and provided protection for the weapon positioned inside it - standard was a heavy machine gun. The firing opening in the dome formed a rounded rectangular 'eyebrow' of approximately 10 cm thickness, which protruded some decimetres outside the dome and provided protection for the weapon positioned inside it - a heavy machine gun or cannon. At the rear, at the entrance to the dome, a recess was made in the concrete to allow the dome to be entered. Both the firing port and the access to the casemate, which was located in a recess behind the dome, could be closed 'gas-tight' from inside.

Valuation

The CAST STEEL DOME CASEMATES TYPE G in the vicinity of Fort Spion are of general interest because of:

* Cultural-historical values as part of the New Hollandic Waterline as designed by C.R.T. Kraijenhoff and first realised from 1815 onwards by him, Jan Blanken and major-engineer Willem Offerhaus and subsequently strengthened and improved by others for approximately 125 years.

* Architectural-historical values, in particular as an expression of military-strategic architecture, which is based on the system of: a. the system of inundation and access defence (19th and 20th centuries), b. the race with increasingly powerful offensive means (20th century) c. the system of 'living' field fortification in depth (20th century)

These are components from the period 1939-1940, namely reinforced concrete remains of several standard cast steel dome casemates.

* Ensemble value and situational values as components of the New Hollandic Waterline in general and because of the mutual functional, functionally-spatial and physical coherence with the other components of the complex and with the access of the Bloklaan.

* The components are representative (characteristic) because they are clearly recognisable as components of a deconcentrated defence line and as defence of an access added to the existing fortification system and also (clearly) preserved as such in the field.

* The components are reasonably well preserved because multiple physical characteristics, despite wilful partial dismantling of the casemates, have remained recognisable.