The topography of a battlefield will determine a commander’s considerations. Topography defines how a position will be defended, dictates tactics, weapons used and where they are sited and the direction in which an attacking force can advance from. It either affords observation or provides cover from observation, it can provide cover from fire or present good fields of fire. A forward slope provides excellent arcs of fire and observation for small-arms such as rifles and machine-guns and allows in-depth positions to mutually support, firing over the top of forward defences. However, when under the direct observation of an artillery observation officer with massed batteries of artillery at the end of a telephone it can become a death-trap.
The Great War first came to the Somme during late August 1914 following the Battle of La Cateau on the 26th. After the engagement the British and French Armies had separated as they retreated back to defend Paris. In pursuit and swinging out west, German First Army advanced across northern France. Its vanguard units cut an axis of advance through Bapaume and on to Albert. The flanks of German IV Reserve Corps passed through Montauban, Maricourt and Carnoy with the advance continuing as far west as Amiens, before turning south towards Paris. Between 5 to 12 September the Battle of the Marne was fought east of Paris, yielding no decisive victory for either side. Stalemate resulted in the opposing forces attempting to out flank each other in a race north, the German army arriving back in the area of the Somme and Montauban during the last week of September. Between 26th and 28th a vicious battle ensued between troops of French 11th Division positioned on Maricourt Ridge and 22nd Bavarian Infantry Regiment holding Montauban Ridge. These initial struggles were fought for control of the high ground. The French could not afford to lose the high ridge on the north bank of the Somme as its loss would result in the Bavarians acquiring observation for many miles over French positions. Likewise, the Germans knew the tactical importance of the Maricourt - Bois Francais Ridge. In an attempt to force the Bavarians back, there by lessening the vulnerability of their position, the French attacked. Their objective was twofold; firstly the capture of Montauban Ridge and secondly Pozières Ridge, the highest ground in the region. After several days slaughter the fighting slackened, both sides exhausted and out of reserves. The final defensive lines were now determined, trench lines were dug and established. Between the River Somme and Mametz they would stay virtually the same for the following twenty-one months of siege warfare. French and German troops settled down to what we now know as static trench warfare. When compared to other areas of the Western Front the area soon became a quiet sector.
During early summer 1915, following a disastrous first half of the year for the French, the British Army commenced taking over the northern zone of the Somme sector, relieving their ally in an effort to reduce the pressure upon their forces whilst showing a firm commitment to the war on the Western Front. A new British army group, Third Army, was formed to implement this task. The Somme front was divided into two Corps zones – a southern sector from the River Somme - Ovillers became the responsibility of X Corps. The extreme right ‘divisional’ sub-sector stretched from Fargny Mill on the banks of the Somme to the Tambour, just west of Fricourt. During early August 1915 British 5th Division relieved French troops, taking responsibility for the whole sub-sector. During the next five months X Corps garrisoned the trenches. During March 1916 the newly formed XIII Corps took over the right of the line, with X Corps side-stepping left.
Only one further readjustment of the line would take place before the ground over which XIII Corps would attack was fixed. On 5 June, French XX Corps took over the right of XIII Corps. The section of front handed over to the French ran from the River Somme at Fargny to the Maricourt - Longueval Road close to the north-western edge of Maricourt Wood. The new front line of XIII Corps, which was on the right flank of the British Army, now extended from Maricourt - Longueval Road on the right to a point midway between Carnoy and Mametz on the left, a distance of 4,000-yards (3,700 metres).
The first line defensive system of both the British and Germans lay mainly on the northern slopes of Carnoy Valley. German trenches were generally positioned higher up the slope, which ran back to the crest of Montauban Ridge. British positions ran lower down the gradient on the same feature.
The sector was dominated by two ridges. Montauban Ridge (140m) occupied by the Germans and Maricourt Ridge (124m) held by the British with Carnoy Valley running between the two. The crest of Montauban Ridge ran from the southern aspect of Trônes Wood, west to Bernafay Wood, through the main street of Montauban village, and then along the Montauban - Mametz Road before sloping gradually down to Mametz village where it meets the west of Carnoy Valley. Three key spurs ran generally south from the crest of Montauban Ridge. To the east, Hardecourt Spur fell from Trônes Wood through Maltzhorn Farm and down to Hardecourt village. Along this easterly spur ran a German intermediate trench which accommodated many observation posts, most of which were manned by German artillery observers. In the centre, a wide spur with a slight gradient dropped from the crossroads close to Montauban Brickworks, sloping downhill in an easterly direction to the edge of Maricourt village where it joined with Maricourt Ridge. From the Brickworks (139m) on the highest point of the spur Germans troops had a clear view over their own trench system and across No-Man’s-Land to a point where British and French trenches met. In the west, a third wide spur ran from the western edge of Montauban down to Carnoy village. This spur was slightly convex at the point where the two opposing forces met. Whichever side held the crest of the convex held the advantage of observation over their enemy’s positions. Opposing lines were very close, the British denying the enemy a view and the Germans pushing as far forward as possible in an attempt to attain observation into Carnoy Valley. As with virtually everywhere else on the Somme front where trench lines were in close proximity and the geology allowed, underground warfare had commenced. The result was a crater field created by the detonation of underground mines which stretched from the west side of Carnoy - Montauban Road east for 240-yards.
Between the spurs lay three re-entrants or small valleys. Two western re-entrants, The Loop - Bay Trench re-entrant and Train Alley sloped down into Carnoy Valley and the eastern re-entrant, known later as Chimpanzee Valley ran southeast into Hardecourt Valley. Train Alley, named after a pre-war light railway line, ran from its source south of Montauban, initially east to west then close to the German first trench it changed direction south to join with Carnoy Valley. Where the re-entrant inclined south of Montauban, a steep bank on its northern aspect created one of only three positions within the German defences where dead-ground could not be observed from any location within the British lines. German pioneers took advantage of these locations, digging deep dugouts beneath the bank. At the location where Train Alley turned south, a second smaller re-entrant spurred off in a north-westerly direction. Although only minor, it also contained a steep sloping bank on its northern face. As with the bank in Train Alley, this small re-entrant was in dead-ground and housed a nest of deep dugouts known as Dug-out Trench and The Warren. The position would prove to be a hard nut to crack for 18th (Eastern) Division and from it German machine-guns would rake the left flank of 30th Division on Z Day. The remaining re-entrant in the German lines ran from a position known as ‘The Loop’ to the German first line at Bay Trench. On the south facing slope of this re-entrant ran a long German trench, ‘Pommiers Trench,’ which overlooked the re-entrant from the north and also protected an approach route to Pommiers Redoubt, located higher along Montauban Ridge.
Along the crest of Montauban Ridge, Montauban village itself had been fortified with many cellars reinforced and extended. Along the ridge a redoubt, already mentioned, known as ‘Pommiers Redoubt,’ named after a few apple trees close by, had been constructed to protect the south-western slopes. On the reverse slope of Montauban Ridge ran a long east-west communication trench named ‘Montauban Alley.’ It allowed lateral movement unobserved from the British held ridges. Beyond Montauban Ridge lay a wide valley entitled Caterpillar Valley, named after a long strip wood of the same name. The valley allowed a reverse slope position for many German field artillery batteries.
Apart from the already mentioned three areas of dead ground, the whole German first line trench system lay on a forward facing slope, whether that be on the spurs or in re-entrants. It was under direct observation from the British held Maricourt Ridge and Hill 124. On taking over the sector from the French, the 5th Division described the area:
Observation was excellent from our positions, the whole of the enemy’s front-line system and much of his rear areas being plainly visible, in this respect we had the superiority, as, owing to the high ground in rear of our forward positions, practically the whole of our back areas was free from enemy observation except from balloons and aeroplanes.
German positions constructed on the forward slope offered both topographical advantages and disadvantages to its defenders. Advantages lay in the observation it afforded over their own and the British trench system. However, not all of XIII Corps’ trenches could be observed by the Germans, especially those where the slope was convex in shape. From their third trench the Germans could mutually defend / support their second (support) and first trench with machine-guns, rifles and mortars as well as using artillery controlled and corrected from artillery observation posts. Their primary disadvantage was that which 5th Division had discovered when taking over this sector; it was almost entirely, except for the three small areas of dead ground, under British observation from Maricourt Ridge and Hill 124. Thus, whatever side dominated the battlefield with a superiority of artillery was the most likely victor.
XIII Corps’ rear area immediately behind Maricourt Ridge sloped away via a number of valleys and re-entrants falling down to the direction of the River Somme. Only one small area remained an open expanse of land, a wide flat spur that ran from a point midway along Maricourt Ridge steadily down to Bray-sur-Somme. On this wide spur and under partial German observation from only the very highest points on Montauban Ridge were two farms, Billon and Bronfay. These farms were situated on the only good road between British rear areas and the forward zone. They were to become staging posts, housing command centres and medical facilities on the main supply and evacuation route to and from the front line. They would also be a magnet for German artillery. Valleys and re-entrants running south from Maricourt Ridge provided considerable cover for British and later French artillery and all other supporting units and logistics. The largest valley, Suzanne Valley, ran directly south from Maricourt village for two miles to the picturesque village of Suzanne. The valley would be the main area for British and French artillery. By late June 1916 its fields held hundreds of artillery guns and howitzers, all located out of view from German observation, except from aircraft or kite balloon.
German defences opposite XIII Corp consisted of a front position of several trenches with a recently dug reserve line. The in-depth reserve line ran between and incorporated Dublin Trench to Pommiers Trench via Train Alley and lay 700 -1,000 yards behind the first trench. The front system was comprised of a first trench and support trench, interconnected with numerous communication trenches, some of which also encompassed fire steps. The whole system was supported and strengthened by numerous strongpoints and redoubts. These strongpoints as a rule provided all round defence and were isolated by belts of wire entanglements and trench blocks. Their garrisons were housed in deep dugouts. On the east flank ‘Dublin Redoubt’ located in the reserve line bolstered the defence of Maricourt Spur. From its slightly elevated position it had unhindered views across to the German first trench and No-Man’s-Land to Maricourt Wood. It also protected Montauban from an enemy approaching via lower ground through Hardecourt Valley and Faviere Wood. Eight hundred yards east ‘Glatz Redoubt’ protected the frontal approaches to Montauban. Like Dublin Redoubt, Glatz offered an unrestricted view over German trenches to the British front line 1,000-yards south. To its west and north, it watched over the lower ground of Train Alley. On its northern perimeter deep dugouts were located on a slight reverse slope, their entrances invisible to the British. Across on the opposite slope of Train Alley were a series of smaller strongpoints; The Warren, The Castle, and The Loop. The Warren was a reverse slope ‘warren’ of dugouts and emplacements that covered approaches up Train Alley from the east. The Loop was positioned close to the source of a re-entrant on the lower eastern slopes of Carnoy Spur. The location could only be observed from Hill 124 and observation posts on the east of Bois Francais Ridge. From this strongpoint its garrison could defend the re-entrant running down to their frontline at Bay Trench and enfilade the British first and support trenches between Carnoy - Mametz Road to Mansel Copse. The Castle, a series of trenches west of Carnoy Craters was positioned on the crest of Carnoy Spur between the latter two strongpoints. From its dominating location, 200-yards in-depth of the German support line, it could defend Carnoy Spur on three sides. The final redoubt in the sector was the previously mentioned Pommiers Redoubt positioned on Montauban Ridge midway between Montauban and Mametz. Literature on this area often describes Pommiers as a position that dominated Montauban Ridge with good observation over the whole sector. In fact, from the forward edge of the redoubt observation, except from one advance sap, was no further than 200-yards. The main redoubt sat in a small depression which hid the position from all British ground observation. Its defence rested in its invisibility to accurate artillery observation, belts of protective wire entanglements, and Pommiers Trench protecting its approaches. The late construction of Pommiers Trench, running midway down the same feature, was undoubtedly created to defend vulnerable approaches to the redoubt.
There was one aspect of the German defensive position that was severely lacking. Between their support and reserve lines and running back to their rear areas there were very few communication trenches. This deficiency in the failure to construct multiple communication routes between their rear and forward defences would have severe consequences once the Allied bombardment commenced. As a comparison, to the German seven communication trenches, the British opposite had constructed twelve main and numerous other inter-connecting communication trenches servicing the same distance of lateral defences. Further north Germans defending Serre had dug a communication trench every 300-yards, compared to an average of every 500-yards in this sector.