It could take as little as three minutes from the time the enemy
was spotted by the observers until they were fired upon. There were
three types of observations posts. Each block, or casemate, had two
observation domes, one the surveillance position, manned by an officer
equipped with binoculars with which to constantly scan the ground.
The dome on the opposite end of the block was manned by an NCO, whose
mission was to register any targets spotted by the officer. The NCO
used a powerful 21cm periscope in the roof of the turret. Closer to
the frontier were auxiliary observation posts manned by one person
with a periscope. The third type of observation post was
located at the entrance of the block or casemate and protected the
casemate itself from attacking infantry. Each observation dome had
three openings, called embrasures, which held periscopes, automatic
rifles, or 50mm mortars. Each observation dome was reached by a ladder
and the floor could be raised or lowered to suit the height
of the observer. They were connected by telephone to the
artillery or infantry command post.
In case of attack, the officer would identify the target and, using
a panoramic photograph, notify the command post of its bearing
and elevation. The NCO, listening through an acoustic tube
would pinpoint the exact coordinates and pass this on to
the command post. A telephone operator would receive the message
and write the information on a blackboard. The command post staff
passed on the information to the artillery commander, who decided
whether or not to fire, and if so, which block would be detailed to
fire. Information was then relayed to the chosen block's commander,
who was in the same room as the artillery commander.
The block commander gave the order for the number of rounds, type of
shell, and fusing. This was passed to the gunlayer by means of a
pointing mechanism revolving around a dial, like on a ship's bridge.
When the "ALERT" signal was given, the gun crew would go to their
positions, the airlock door
leading from the main gallery to the base
of the combat block was closed (each block had its own airlock system,
consisting of two sets of doors), the interior air pressure mounted to
keep fumes from reaching the galleries, and the turret was raised into
the firing position. Shells were taken from the racks in the lower level
of the turret, placed into the hoists, and lifted to the firing
chamber. There, four men, two layers, and two loaders, cramped
under the cupola roof, manned the guns. The turret was turned to
face the target and the gun elevated. The shells were placed in
the breeches, the gun was fired, the breeches were opened,
and shells ejected. Once finished, the observers reported the
results.
Gun crews were on a three-watch system - duty, stand-by, and rest.
Combat personnel were kept in the first two statuses. Those on
stand-by joined those on duty when the alert sounded. The garrison
found that it was best to stay at the blocks rather than trudge sometimes
long distances back to the barracks, although the barracks were
the only place to get uninterrupted sleep during the constant
firing. The officers had no relief as they were on duty day and night.
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