Fortress Artillery 1914-18
by Robert Robinson

The number of different types and makes of gun to be found in World War One forts and fortresses is very great and is a reflection of the many different countries involved and the range of ages of the forts themselves.

Thus any one of the great imperial powers might have both forts in key places that were armed with the latest heavy guns and mountings and, in remoter, quieter, corners of the empire, forts that still mounted huge muzzle loading guns that would not have looked out of place in Fort Sumner or Vicksburg. In addition the same gun might appear on a variety of different mounts (the British series of 9.2 inch guns, for example, were exported to many countries and used on almost every kind of mounting it is possible to conceive). It would require a work of book size to contain details of every gun and mount.

It is, however, possible in a shorter work to define some broad classifications.

1. Field guns

Although not well suited to a fortress situation, field guns were sometimes used to supplement the fixed armament of a fort. Firing from their normal carriage they would be most usually placed in outworks pointing over a low breastwork and used for direct fire anti personnel purposes.

Such guns suffered from a number of disadvantages. Their angle of depression (ability to shoot down from a height) was often very limited and their crews were very vulnerable to overhead fire.

2. Wheeled Garrison or Fortress Carriages

In the heyday of the smooth bore muzzle loading gun all fortress guns were mounted on low, small wheeled, carriages very similar to those used on board ship (except that garrison carriages usually did not have wheels or trucks at the rear of the carriage). In peacetime the gun would be mounted on an iron carriage but in time of war the wooden version would be reclaimed from the stores and the gun remounted. Such guns would be pointed out through embrasures or gun ports. A battery of such guns would look very much like a stone version of a man o war’s lower deck.

Such guns were obsolete by 1914 but some survived in odd backwaters. However there was one form of wheeled fortress carriage that did survive to be used in World War One. This was the tall garrison carriage (sometimes with large wheels) that enabled a gun to be fired over a high parapet. These were often used to mount early breech loading guns before the introduction of recoil mechanisms. Some of these guns survived in older forts.

3. Pivoting guns

As guns became heavier and more powerful the wheeled garrison carriages had become inadequate and were replaced with mounts in which the gun recoiled along a slide. Initially the recoil was often damped by the use of friction devices (such as ‘squeeze’ plates) or by simple gravity (by inclining the slide up to the rear). As hydro pneumatic recoil systems were developed these supplemented or replaced the older, mechanical, recoil dampers.  To point the guns the carriage was mounted either on a very heavyweight pivot (or turntable) or with one end of the carriage anchored to such a pivot, in the latter case with the ends of the carriage fitted with supporting wheels at an angle. These wheels were sometimes flanged allowing them to move along a curved rail.

Such guns might be fired from casemated batteries; this gave the guns and their crews good protection against enemy fire. This type of gun emplacement was still being used in World War Two. However in situations where the gun had to be able to traverse a wide arc (typically wider than 90 degrees) the casemate system could not be used. Such situations often faced coastal forts needing to be able to track moving warships over a wide stretch of defended water. In such cases the guns were placed in the open behind a curved parapet over which they fired or in a shallow gun pit. In both cases the gun crew was exposed to overhead fire at all times and direct fire when loading the gun.

The Turkish Dardanelles forts used this type of emplacement and the crews suffered very heavy casualties from the fire of British and French warships. At least one of the German forts (Fort Bismark) at Tsingtau had heavy guns emplaced in this manner and also appears to have suffered badly from Japanese shelling (in this case from heavy land based siege guns). Some US coastal forts had similar gun emplacements and would doubtless have had the same problem had they ever come under attack. Comparable mounts were to be found in fortifications in the unoccupied part of Belgium and in Russia as well as in neutral Norway

With the introduction of effective recoil systems at the end of the 19^th century it became possible to mount smaller, quick firing, guns on pedestal mounts. Six pounder (or 57mm) QF guns were a frequently found in this category. A typical emplacement would be in a casemate behind a curved armoured shield that rotated with the gun, not unlike the 6 pounder installation on a British tank of the period.

4. High Angle Guns

As many unfortunate fortress garrisons were to discover plunging fire is an effective way of penetrating armour be that concrete of steel. Some forts did have high angle guns that could themselves deliver plunging fire. A number of American coastal forts were equipped with huge long barrelled, rifled, breech loading, 12 inch mortars that could deliver devastating blows to the relatively thinly armoured decks of battleships and battlecruisers. Typically these guns were housed in large pits in groups of four.

Each mortar was mounted on a turntable. Although there is no record of them being fired in anger in World War One such mortars were used in 1942 in the defence of Corregidor. In a battle situation the crews of the mortars would be totally protected from direct fire. However if the enemy could deliver overhead fire they would have been in considerable danger. The concrete walls of the pit would amplify the blast effect of a shell landing in the pit. As it was even practice firing of the mortars was dangerous to the health of the gunners as the shockwaves from the discharge were reflected back from the concrete walls of the pit.

It is possible that the Skoda 302 mm howitzer was turntable mounted in some Austro Hungarian forts. This would certainly have made life unpleasant (and probably short) for any attacker trying to dig in siege guns.

5. Disappearing Guns

These originated as a development of tall garrison carriage. The approach invented by a Captain Moncrieff of the Edinburgh Militia utilised the recoil of the gun to raise a counterweight and swing the barrel back and down. A catch locked the gun in position at the end of the down stroke and was released, after loading, to allow the counter weight to swing the gun back up to the firing position. The counterweight system was soon replaced by a number of hydro pneumatic systems one of the most successful being that produced by Armstrong’s Ellswick Ordinance Company (EOC) first introduced in the 1880s.

It could be very effective, a trial was carried out in 1885 using a full sized ‘working’ wooden model that was raised and lowered from behind a rampart to simulate firing whilst HMS Hercules attempted to hit it with the ships guns. After 100 rounds had been fired no hits had been made on the disappearing gun (in reality Hercules would have been sunk long before). A typical gun mounted on the later versions of this carriage was the British 6.6 inch although guns of up to 11 inch calibre were mounted on such carriages. The carriage would typically be mounted on a turntable.

These EOC disappearing carriages were in production until 1912 being being installed in coastal forts all around the British Empire. This was partly the result of a series of ‘Russian scares’ when it was feared that the Russian Empire would attempt to expand into the Pacific at the expense of British, Australian and New Zealand territories. Although the British Army declared the mount obsolete in 1911 many such guns were still in service in World War One. The US Army utilised disappearing carriages using the Buffington Crozier system that used both a counterweight and hydro pneumatics.

Disappearing guns were installed in a string of coastal forts on both Eastern and Western seaboards as well as in Hawaii and the Philippines. In 1917 many of the guns on the Pacific seaboard, where there was no naval threat, were dismounted and sent for service in France being remounted on ponderous but conventional gun carriages. They were returned and remounted after the war. America kept its disappearing guns in service up to and during World War Two, six forts equipped with these guns taking part in the defence of Corregidor in 1942.

One of the potential problems with these guns was exposure to overhead fire. This was in part resolved by emplacing the guns in circular pits with an overhead shield pivoting with the guns turntable. This shield had a gun shaped slot through which the gun would rise and fall. Such a system provided the gun crew with a measure of protection. However photos suggest that most American guns were not protected from overhead fire.

6. Barbettes

By the beginning of the 20^th century many considered the disappearing gun system to be too complex and also one that it hindered rapid fire (which could only be as fast as the time taken for the hydraulics to allow the gun to recoil down and rise back). A replacement system (possibly borrowed from battleship design) was devised. This was the barbette system in which a pivoting gun was placed over a roofed in pit. This roof (often armour plated) was pierced to allow a shell lift to feed ammunition to the rear of the gun breech where it could be rammed home. The lift and the roofing plate usually rotated with the gun. Effectively the gun was installed behind a parapet and on top of a sunken turret. The handling of ammunition (preparation of charge, fuse setting etc) was carried out in the relative safety of the pit. The original gun pit could often the utilised.

A gun shield was often fitted to provide those of the gun crew remaining above the barbette with some protection. From 1911 the British Army, began to replace disappearing guns with barbette mounted weapons. The process of replacement was by no means complete by 1914 although many of those disappearing guns on the British mainland were so treated. The American Army also used some barbette mounted guns in coastal forts, especially where the gun to be mounted was considered too big for the mechanism of a disappearing mount to handle. A good example of this was the forts protecting the Panama Canal where barbette mounted 16 inch guns were installed. Some Russian forts appear to have been fitted with Barbette mounted guns.

7. Cupolas and Turrets.

In 1882 a combined British and French fleet bombarded the Egyptian fortified batteries at Alexandra. Although the batteries out gunned the attacking fleet in terms of the number and weight of the guns the result was a disaster for the Egyptians. Although the fortress gunners were protected behind substantial ramparts and parapets they (and their magazines) were completely exposed to overhead shell fire, which is precisely what the attacking fleet delivered. The lesson was not lost on military strategists and planners around the world began to seek ways of protecting guns and their crews from modern shell firing weapons. An obvious solution to the problem of protecting a gun from overhead fire is to house it under an armoured cupola or in a turret (much as in a warship). In the next few years a number of such products were designed and demonstrated.

The Schumman-Gruson chilled iron cupola was demonstrated in 1885 and patented in 1886. It was immediately adopted by Austria-Hungary, Belgium, Germany, Italy and The Netherlands. Rival turret and cupola systems were produced by Schneider and Skoda (unsurprisingly France adopted the Schneider system and some Austro-Hungarian forts were later fitted with the Skoda system). General H.L. Abbott made a report to the American Academy of Science warning of the inadequacy of US coastal forts and their vulnerability to a British naval assault based on nearby Bermuda (a sort of 19^th century Cuban missile crisis) and suggested, amongst other things, the adoption of heavy guns in cupolas.

The US Congress looked the idea, they also looked at the cost of such systems and nothing was done. Objections to the concept were raised in Britain, the argument being that the cost of such systems would result in forts relying on a concentration of small number of heavy guns which, if knocked out, would leave the fort useless. The same expenditure could have been used to provide a much larger number of heavy casemated guns.

Nevertheless cupola systems were adopted on almost all modern forts around the world.

When the test of war came the various systems were very largely found wanting. The armoured cupolas proved not to be proof against heavy siege artillery and could be knocked out by a direct hit. Near misses could penetrate the surrounding concrete or masonry and jam the turret mechanism. Sometimes just the sheer weight of the cast cupolas was too much for the components and bearings of the traversing mechanism. Many pictures of fallen forts show shattered cupolas and uprooted turret bodies.

Worse still a central magazine was the almost inevitable result of the concentration of guns. If this went up so did the fort. Even before Italy entered the war, a magazine explosion destroyed one Italian fort. An investigation suggested that this was due to sloppy practice in the handling and priming of ammunition resulting in a shell with a primed percussion fuse being dropped. One of the Liege forts was destroyed in 1914 by a German heavy shell penetrating the concrete and detonating in the magazine; half the garrison lost their lives in the explosion. In 1916 exactly the same fate befell an Italian fort when a 305mm shell struck just behind the main gun cupolas and passed all the way through the concrete to the magazine.

The turrets fitted to French forts at Verdun were better at surviving. Key factors in this may have been the use of armoured steel in the Schneider turrets (rather than chilled iron as in the Gruson turrets) and the use of reinforced concrete (ferro concrete) both of which were better able to resist heavy shells.

Smaller medium artillery and machine gun turrets were fitted to many forts, usually acting in an anti personnel role. A number of companies (including Gruson and Krupp) produced these more or less as an off the shelf product (so that a fort builder could effectively go along to ‘Merchants of Death R Us’ and choose the secondary turrets he wanted.).

A further refinement was the retractable or disappearing turret. These employed counterweight and hydraulic mechanisms that allowed the turret to sink after firing so that its top would be flush with the carapace of the fort. This reduced the chance of a strike on the side of the turret but did nothing to help with a plunging shot hitting the top of the cupola. Even if this did not destroy the turret it would stand a very good chance of jamming the raising and lowering mechanism and thus putting the turret out of action. Possibly as a result of the great weights involved, these mechanisms appear to have been temperamental and prone to jamming even without the hazard of shell fire.

Smaller retractable turrets were developed (usually for guns of about 75mm) but not just for artillery – retractable searchlight and machine gun turrets were also fitted to some forts. These might remain retracted until an assault on the fort was attempted and then unmask themselves. Such turrets were developed further in the inter war period some being incorporated in the Maginot Line (and later salvaged for use in various German defensive constructions).

In some cases Fort turrets resembling those found on ships were used. These were usually for smaller, secondary, armament although in the post war period the Americans went the whole hog and fitted battleship turrets to at least one fort (Fort Drum).

This overview of fort armament would not be complete without the mobile turret or Fahrpanzer. This was a Gruson armoured turret with rapid firing gun (57mm), which could be moved on four small wheels along a 60cm narrow gauge railway inside the fort. They were used in both German and Austro Hungarian forts. Typically the rails would be in a trench or behind a thick concrete parapet so that only the top, rotating, part of the turret was exposed to the enemy.

One has a picture of them proceeding along like ducks in a fairground shooting booth. However the role of the rails and wheels was to allow them to be moved quickly where they might be most needed. They could be ‘parked’ completely concealed behind part of the fortress wall and only trundle into view just in time to repel and assault. The Fahrpanzers were designed to be easily transportable by a horse drawn vehicle so that they could be quickly deployed outside the fort itself. They were used in field and trench works on many fronts. When used in this manner they were usually emplaced as fixed turrets.