... And finding a Trench Map error.

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LOCATING THE FIRING SITE

In 2020 our GWF colleague Ian Jones researched and published a super blog article on "The King's Shot", describing how King George V attended the live firing of a 14" shell from the "Boche Buster" railway gun on the 8th August 1918.

But where exactly was the gun located when the shot was fired? This article looks at evidence to confirm the location - and finds that the Army map makers at the time incorrectly plotted the location as a narrow gauge line that would never have managed to carry such a large gun.

The war diaries / shooting reports for 26th HAG show that the railway gun was located near to Maroeuil Station, north west of Arras, on the 8th August 1918 with the primary target being Douai Station, approximately 20 miles away..[1]   When in firing position, such artillery pieces could not remain on a main line, so they were run onto branch lines that were often specially built for the purpose. "Boche Buster" had only +/- 2 degrees lateral aiming motion on its railway mount, so the main targetting was done by positioning of the gun wagon on a curved branch spur. In the days before a major shoot, plotting officers would calculate precisely where the gun carriage had to be on the curve and would mark the rails so that wheels were exactly at the right spot.

Hence, using maps, we are looking for a curved branch spur from a standard gauge railway line near Maroeuil with the ability to align the gun to point at Douai, on a bearing just north of due east.

Film of the King attending the gun is available courtesy of IWM and that gives clues about the firing site that need to be considered. These include the fact that the railway branch is curved and stops short of a road; there are buildings visible in various directions; and another stretch of standard gauge line runs jointly close to the branch.[2]

Using the TrenchMapper system available via the WFA, alongside Google Maps in Satellite mode, it is possible to search for candidate locations.

In previous days "Boche Buster" had been garaged at Savy-Berlette on the line from Arras to St Pol and the gun had been reported firing at Fond de Vase, which lay on a standard gauge line between Maroeuil and Thelus, due north of Arras. So by tracking along the railway line between Savy and Fond de Vase using the mapping tools, it is possible to look for likely locations.

Google Maps proved to be the source of the most likely site, with a scar visible on ground that lies between Bray Woods and the town of Maroeuil.

The main railway line still operates today and is visible running from top left to bottom centre right in the picture, lying between hedgerows. A field track runs alongside west of the line and the Bray - Maroeuil road is to the east.  At the centre of the image a curved mark runs across the fields and forms a triangle with another straight mark. The mark stops just short of the River Scarpe and the Bray road.

To cross-check that this is the right place we use Trench Mapper to see if there is a map available around the date of the shot.

The map of the 6th May 1918 does not show any feature that matches the triangular scar - and nor does the French map of 28th May.

Both show  a 60cm W^D Light Railway line running across the fields just west of the standard gauge line, notably in the gap next to a field with a marked right-angle corner. That field can still be seen on Google Maps today.

However, the railway gun branch is marked on the 1:20,000 map "51C NE Aubigny Harbarcq 4C Local trenches corrected to 20 July 1918", so the branch spur looks to have been constructed during June/July 1918. That ties in well with the facts from WO 95 that the railway gun had arrived in France on the 26th May with 471 Siege Battery and had been allocated to 26th HAG on the 8th July. [3]

(**** Update - it is now clear that the spur was constructed earlier, possibly in 1917 - see comments and German maps below ****)

It would be nice to cross check with a map reference from the day, but unfortunately the 26th HAG shooting reports (TNA WO 95/218/4) do not give grid references of firing sites. But there are clues in the film taken of the King's visit to see "Bocche Buster" in action that help to confirm that this is the right location. The following stills show key features and then a diagram maps those features to the location.

Looking more closely at the 20 July map we can see that the Army cartographers made a mistake in their plotting of the new branch spur. "Boche Buster" was a huge, heavy monster of a gun and ran on standard gauge railway track. The modern satellite view clearly shows that the spur connected with the main railway line. But the map makers have drawn the branch as a 60 cm light railway, drawn in red with short marks crossing regularly.

The mapping offices had huge workloads to issue regular updates to the many trench maps that were needed for military planning, so inevitably some errors crept into the final product. By 1918 the use of aerial photographs was well advanced and we can imagine that whoever interpreted the new railway feature at Maroeuil made a quick assumption that any change must have been to the highly flexible light railway rather than to a main route. Their focus was probably concentrated on edits needed to marked enemy trenches rather than odd additions behind the Allied front line.

The branch looks to have been purpose built to keep firing at Douai Station on a regular basis. Douai was a key junction for the Germans to move men and supplies southwards and would be an important target. That perhaps explains why a large building is marked on the map beside the branch spur. The railway gun needed supplies of shells, each weighing three-quarters of a ton, and hefty cordite charges, along with maintenance facilities. The crew needed food and accommodation, and the officers needed working space for range plotting. The gun itself would normally be returned to Savy for garaging after a firing session.

A special ammunition wagon had been built by Armstrong-Whitworth that carried up to 128 shells and that had a special hoist mechanism to feed each shell to the rear of the railway gun for loading. And the complete train needed if the gun moved to a new firing site included the ammo wagon, cordite wagons, one or two officers' wagons, an artificer's wagon, diverse supplies wagons, several French "40 Hommes 8 Chevals" wagons for the crew's accommodation, and a guard/brake van. So it is likely that putting much of that capacity into a building on site would make it easy to run a much shorter train from Savy-Berlette on the accasions that "Boche Buster" was to fire from the Maroeuil spur.

One aspect to consider is that the new branch had to cross the line of the existing light railway. There were some standard ways of addressing that issue used by the Light Railway Operating Companies, including an angled crossing-point junction for the two different gauges, or even putting a lifting section into the 60 cm track - see the excellent books by Roy Link "WDLR Album" and "WDLR Companion" for further details.

Looking more closely at the ground today it can be seen that the second straight line alongside the curved arc served two purposes. Firstly, there was a "run-around" at the end of the line by the River Scarpe, which allowed a locomotive that may have hauled the gun into position to move away from the front of the gun and back into a safe area. The line also enabled supply wagons to be manouevered to the buildings.

THE SITE TODAY

Given that the line of the branch spur is visible from above, what does it look like on the ground today?

The next images, thanks to Google Streetview, show that the rail embankment is clearly visible from the Bray-Maroeuil road.

The River Scarpe lies between the site and the road, making access difficult at this point. However there is a field track that runs from close to Maroeuil Station into the pasture field where the emabankment is located, so on my next visit to Arras I plan to go and take a look.

HITTING THE TARGET

Lastly, as Ian reported, it is believed that the King's Shot was a direct hit on Douai Station. By switching from Google Streetview to Google Earth it is possible to plot the ground trace of the shell's trajectory. The fire plotting officer would have a good idea of the places that lay under the shell's flight path, but the crew would just know that the gun was aimed somewhere over the direction of Thelus. 

The railgun wagon had been aligned on a tangent to the rail arc that aimed at Douai, with final adjustment on the gun mount.

The distance measurement tool on Google Earth reckons that the shell travelled 28,500 metres. Given a muzzle velocity of around 1000 metres/second, that means the shot took something like 30 seconds to fly to Douai Station. 

On the way it flew past many places known to those familiar with the battlefield between Vimy and Arras, including passing right overhead Oppy Wood.

A remarkable shot by a remarkable gun, managed by a skilled and zealous unit.

 

A few questions remain that I continue to consider and would welcome any additional information:

Is there a war diary for a company of engineers that built the branch line and the building?
Is there a report that pins down how the existing light railway was crossed?
Why does the straight line not re-join the mainline? Did it cross the LR as well? 
Can it be confirmed that the building was for Railway Gun supplies?
 

Thanks gratefully given to Ian Jones for his kind help with information about the 471st Siege Battery; Imperial War Museum {IWM) for making the film of the King's Shot available; The National Archives (TNA) for access to WO95 unit records; Western Front Association (WFA) and TrenchMapper; Google Maps Streetview and Google Earth.

References:

[1] TNA WO 95/218/4 page 100 of 124 26th Army Brigade RGA (aka 26th HAG)

[2] Catalogue number IWM 218:  https://www.iwm.org.uk/collections/item/object/1060008215 from 12:00

[3] TNA WO 95/5494/4 page 216 of 227.