Infantry Blockhouse K-S-5 "U potoka".
Photograph of the infantry blockhouse K-S-5 "U potoka".
View from the left.
Upper Floor (Fighting Floor):
- The main corridor of the upper floor is about 15 m long and 2.40 m high. It is possible to enter eight rooms from here.
- The main armament of the blockhouse was located in the shooting rooms (casemates). The main fire effect was produced by flanking and cross fire. (Frontal fire was not strongly developed, so that the blockhouse depended upon support from neighbouring redoubts.) This main fire armament comprised:
All weapons inside the fortification were installed in special gun-carriages. Therefore their handling was very easy and the accuracy and efficiency of fire was excellent. Empty cartridges were carried away outside the room into a protection ditch. There is one more loophole for gorge fire in the casemate where a light machine-gun Mark 26 (weapon N) was installed, if necessary. Its main task was to hold under fire the space in front of the entrance leading to the blockhouse and peripheral obstacles to the rear of it. Excellent ranging telescopes were used for aiming all the weapons and common aiming using sight and bead could be used in emergency at the same time. Moreover two indirect aiming methods were used: The first one was reporting co-ordinates by the observer inside the bell, the second one used an environmental terrain map fixed to gun-carriages. This map was in fact a panoramic drawing of the terrain in front of the loophole located above it. The gun-carriage mechanism was mechanically coupled with a rider permanently showing the place on the above mentioned map where the weapons were aimed. Apart from weapons inside the shooting rooms there was an emergency store of ammunition, hand grenades for the grenade slide, spare parts for the weapons and important tools for weapon repair. Seven men were needed for tending the arms.
- Weapon L1 - an anti-tank gun Mark 36 (calibre 47 mm / 1.85 inch) coupled with a heavy machine-gun Mark 37 (calibre 7.92 mm / .312 inch).
- Weapon M - twin heavy machine-guns Mark 37 (calibre 7.92 mm / .312 inch) mounted on a common gun-carriage.
Weapons of the K-S-5 Blockhouse Overwiew:
[mm] / [inch]
|rounds per minute
|4 cm anti-tank gun +
M.G. Mk. 37
||47 / 1.850
7.92 / .312
|2x M.G. Mk. 37
||7.92 / .312
||2 x 550
|light M.G. Mk. 26
||7.92 / .312
|heavy M.G. Mk. 37
||7.92 / .312
- Telephone operator room - a small room used by the phone operator and his equipment. From here it was possible to intercommunicate with all other forts of the defence line using an external telephone network. All single rooms inside the object were connected by an internal telephone network as well.
- Commander room - the commander had his own single room. There were a bed, table, a case and a telephone here. Additionally he was able to communicate with his neighbouring operator rooms (see above) using a small window in the wall.
- Stores of the machine-gun ammunition - nearly 450 thousand cartridges of the calibre 7.92 mm (0.201 inch) in small cases in several rooms were stored inside the blockhouse. The same ammunition was used for both machine-gun types. Heavy machine-guns were fitted with bands containing 100 or 200 cartridges. The light machined-guns were fitted with 20 cartridges on the storage bins.
5'. The barracks for officers.
- Space at the end of corridor in the left protective wing - several important equipment are located here at the internal side of the rear wall:
- A small fan (driven both electrically and by hand) for extraction of combustion products from the left armoured bell.
- A pull-up wall periscope for the protection ditch bottom and the blockhouse foreground observation.
- There is one of four embrasures for a light machine-gun (M.G. Mark 36) in the middle of the rear wall. Its task was to keep clean the space in front of both main heavy embrasures (from the room No. 2).
- Closed to the loophole was a sheet-metal box with a kerosene cooker, where the crew could warm up their dishes.
- A grenade slide was directed just into the protection ditch.
- The bells - were made of steel and enabled observation of the blockhouse surroundings and signalling. A pull-up and revolving periscope with quadruple magnification installed directly in the top of the bell was used for terrain observation. The bell loopholes were used both for additional observing and, if the enemy approached close to the blockhouse, machine-guns (one light machine-gun Mark 26 in each flanking block bell and one heavy machine-gun Mark 37 in the front bell) for both front, flank and gorge fire were prepared for the blockhouse defence. There were two types of insets which could be replaced in the bell loopholes:
The ammunition was transported by a simple hand-lift into the bell. The main task of the observer was to control the main weapons firing.
There was a threefold connection to the weapon crew - a voice-pipe, telephone and a light signal equipment if the battle was too noisy.
- Observation insets - for additional observation.
- Defence insets with gun-carriages - for one machine gun (weapon N or D - see above).
- The main store of anti-tank gun ammunition - four types of ammunition were fired by the 40 mm anti-tank guns (code-name L1): Anti-tank grenades, explosive shells, time-bomb shells and grape-shots. Altogether 3600 cartridges could be stored in this room. During the critical days in 1938 there were 2240 cartridges here (62% of maximum).
- Space at the end of corridor in the right protective wing - the internal side of the rear wall is equipped just in the same way as the space in the opposite wing of the corridor (see No. 6): An extraction fan for combustion products from the right bell, a pull-up wall periscope, an embrasure for a light machine-gun and a grenade slide. There is no kerosene cooker here, because there was only one in the whole blockhouse K-S-5.
Lower Floor (Edge Floor):
- Washroom and WC - the blockhouse K-S-5 was equipped with two small WC cabins. The waste from here drained away into a sump located under the WC cabins. This sump worked in fact as a slot cleaner where the waste was biologically decomposed. Partially cleaned water drained away through a pipe on the ground of the trench. The nose of this pipe was protected by a so-called "frog flap". The biological gas generated during the sewage digestion was disposed of by a special pipe outside the blockhouse. The sump sediment was pumped away from time to time.
- Rations store for the crew - rations for the crew during the fight for two weeks were stored in this room. What was prepared for soldiers to eat? A daily ration contained one soup, one meat-tin, 500 g cracker bread, 0.05 litre (0.1 pint) rum and 50 g chocolate. There were cigarettes in the store, too. The crew received 20 Zora cigarettes and the officers 20 Egypt cigarettes.
- Earth telegraphy room- the earth telegraphy was a wireless liaison system using electromagnetic pulses transmitted through the earth. Its maximum range was 2 km. This system was attended by one man who had his own bed in the same room.
- Crew barracks - 38 soldiers of the 11th troop of the 6th border regiment operated the whole blockhouse. They were allowed to use two-storied beds on which they changed because one half of the crew had to fight while the other one took its rest.
- Fuel store for Diesel engine power supply - about 1000 kg (2205 lb) of diesel oil and 100 kg (220 lb) of lubrication oil was stored here. Harmful vapours from this room were extracted by a small extraction fan in the neighbouring machinery room (No. 15).
- Machinery of the blockhouse - there was a Diesel engine power supply on a concrete stand just in the middle of the room. Its output power was about 8 kW (11 HP). This power supply was the only supply of electricity mainly needed for electric motors of fans and water pumps even if all of them were equipped with emergency hand drives. The electricity was used for illumination at the same time. Corridors were conservatively illuminated with l5 W electric bulbs, only the commander room, the shooting rooms and the machinery were equipped by 25 W bulbs. A small fan in this room extracted vapours and odours from here and from the neighbouring fuel store (No. 14) of both diesel and lubrication oil.
- The hand grenade and the lighting rockets store - time grenades Mark 38 should have been originally used for the grenade slide. In September 1938 only common impact grenades Mark 34 were available. White rockets were used for lighting the blockhouse surroundings and the colour ones for signalling.
- There is a deep well in the blockhouse and thanks to the fact that somebody unknown had covered its neck by a piece of metal-plate, it is well operable up to the present day. Its depth is 24 m (according to a measurement in 1994). The water from this well was pumped into tanks over the stairs by a motor pump and from here distributed by a gravity feeding tube system.
- The filtration room of the blockhouse had a very important function. Its task was to give a permanent supply of fresh air which was of vital importance for the crew and was necessary for the cooling of weapons at the same time. The filtration room was only a part of the whole ventilation and filtration system of the blockhouse. The function of the ventilation and filtration system was based on a permanent excess of pressure inside the blockhouse. This excess pressure discharged the combustion products of weapons through embrasures and prevented the blockhouse from being penetrated by toxic gases (e.g. Yperit, Sarin etc.) from outside at the same time. The weapons of the blockhouse K-S-5 needed 2000 cubed metres of fresh air per hour. This blockhouse was built in 1936, so its ventilation and filtration system was made still in the "old" way. It had a big inlet and a many small orifices in the rear walls. The air was sucked in by an inlet in the small entrance corridor. Its ingenious location disabled holding the inlet under fire and iron grates preserved it from occasional splinters. The air from here was conveyed into the filtering room in the lower floor. Here it was first cleared of some mechanical impurities using three antidust filters. It depended on if that intaken air was pure or contaminated by chemical warfare gas.
AIR-VENTILATION DISTRIBUTION FRAMES
normal operation ++++
Photo of infantry blockhouse K-S-5 "U potoka".
View from the rear.