Eingreif division () was a type of German Army formation of the First World War, which developed in 1917, to conduct immediate counter-attacks () against enemy troops who broke into a defensive position being held by a front-holding division () or to conduct a methodical counter-attack () 24–48 hours later. Attacks by the French and British armies against the on the Western Front had been met in 1915 and 1916 by increasing the number and sophistication of trench networks, the original improvised defences of 1914 giving way to a centrally-planned system of trenches in a trench-position and then increasing numbers of trench-positions, to absorb the growing firepower and offensive sophistication of the Entente armies.
During the Battle of the Somme (1 July – 18 November 1916), the use of defensive lines began to evolve into the defence of the areas between them, using the local troops of the trench holding divisions and (relief divisions), held back beyond the range of Franco-British artillery, to replace front line divisions as they became exhausted. In the winter of 1916–1917, the use of such divisions and the fortified zones between trench lines was codified and divisions trained in the new defensive tactics. Training was based on the experience of the defensive battles of 1916 and the new principles of fortification, to provide the infrastructure for the new system of defensive battle by and (counter-attack divisions).
The new defensive principles and fortifications were used in 1917 to resist the Franco-British offensives. After failures at Verdun in December 1916 and at Arras in April 1917, the system of fortifications defended by supported by divisions counter-attacking from the rear was vindicated during the French attacks of the Nivelle Offensive. The continuation of British attacks at Arras in the wake of the French debacle on the Aisne, led to the highest rate of casualties per day of the war but the system failed again at the Battle of Messines. German defensive tactics reached their ultimate refinement during the Third Battle of Ypres and there were only slight alterations during the defensive battles of late 1918. In the interwar period, German defensive thinking incorporated the new technology of aircraft, tanks, anti-aircraft guns and anti-tank guns in a much deeper defensive system filled with positions for delaying actions, before a counter-attack was made by armoured and mechanised formations.
German defensive tactics
1914–1916
German defensive tactics had been based on the publication of 1906 (Drill Regulations for the Infantry), which expected defensive warfare to be short periods between offensives. On the Somme front, the construction plan ordered by Falkenhayn in January 1915 had been completed. Barbed wire obstacles had been enlarged from one belt wide to two, wide and about apart. Double and triple thickness wire was used and laid high. The front line had been increased from one line to three, apart, the first trench (, battle trench) occupied by sentry groups, the second (, living trench) for the front-trench garrison and the third trench for local reserves. The trenches were traversed and had sentry-posts in concrete recesses built into the parapet. Dugouts had been deepened from to , apart and large enough for
An intermediate line of strong points () about behind the front line had also been built. Communication trenches ran back to the reserve line, renamed the second line, which was as well-built and wired as the first line. The second line was built beyond the range of Allied field artillery, to force an attacker to stop and move field artillery forward before assaulting the line. After the (Autumn Battle) in Champagne during late 1915, a third line another back from the was begun in February 1916 and was nearly complete when the Battle of the Somme began. German artillery was organised in a series of (barrage sectors). The Somme defences were crowded towards the front trench, with a regiment having two battalions near the front trench system and the reserve battalion divided between the and the second line, all within of the front line.
Tactical revision, 1917
Winter 1916–1917
New manuals
After the Battle of the Somme (1 July – 18 November), General Erich Ludendorff had German defensive doctrine revised. On 1 December, the (OHL, supreme army command) published new tactical instructions, (Principles of Command for Defensive Battle in Positional Warfare), in which the policy of unyielding defence of ground regardless of its tactical value, was replaced. Positions suitable for artillery observation and communication with the rear were to be defended, where an attacking force would "fight itself to a standstill and use up its resources while the defenders conserve[d] their strength". Defending infantry would fight in areas, with the front divisions in an outpost zone up to deep, behind listening posts, with the main line of resistance placed on a reverse slope, in front of artillery observation posts kept far enough back to retain observation over the outpost zone. Behind the main line of resistance was a (main battle zone), a second defensive area deep, also sited as far as possible on ground hidden from enemy observation, while in view of German artillery observers was to be built. A (rear battle zone) further back was to be occupied by the reserve battalion of each regiment.
Somme analysis
Erfahrungen der I Armee in der Sommeschlacht (Experience of the German 1st Army in the Somme Battles), written by Colonel Fritz von Loßberg, Chief of Staff of the 1st Army was published on 30 January 1917. During the Battle of the Somme, Loßberg had been able to establish a line of (relief divisions), with the reinforcements from Verdun, which had arrived in greater numbers in September 1916. In his analysis, Loßberg opposed the granting of discretion to front trench garrisons to retire, as he believed that manoeuvre did not allow the garrisons to evade Allied artillery fire, which could blanket the forward area and would invite opposing infantry to occupy vacant areas. Loßberg considered that spontaneous withdrawals would disrupt the counter-attack reserves as they deployed and further deprive battalion and division commanders of the means to conduct an organised defence, which the dispersal of infantry over a wider area had already made difficult. Loßberg and other officers had severe doubts as to the ability of relief divisions to arrive on the battlefield in time to conduct a (immediate counter-attack from the deep) from behind the battle zone. The sceptics wanted the Somme practice of fighting in the front line to be retained and authority devolved no further than the battalion, to maintain control ready for a (methodical counter-attack) after by the relief divisions. Ludendorff added the analysis to the new
Field fortification
(Principles of Field Fortification) was published in January 1917 on which new defensive fortifications were to be based, to provide the infrastructure for the new defensive tactics. By April an outpost zone () held by sentries, had been built along the Western Front. Sentries could retreat to larger positions () held by (five men and an NCO per ), who would join the sentries to recapture sentry-posts by ( (immediate counter-attack). Defensive procedures in the battle zone were similar but with greater numbers of men. The front trench system was the sentry line for the battle zone garrison, which was allowed to move away from concentrations of enemy fire, then counter-attack to recover the battle and outpost zones. Such withdrawals were envisaged as occurring on small parts of the battlefield, which had been made untenable by Allied artillery fire, as the prelude to (immediate counter-attack within the position). Such a decentralised battle by large numbers of small infantry detachments would present the attacker with unforeseen obstructions. The further the penetration, the greater would be the density of defenders, equipped with automatic weapons, camouflaged and supported by observed artillery fire. A school was opened in January 1917 to teach infantry commanders the new methods.
is generally translated as counter-attack but the term has other connotations. In German military thinking, it included a sense of intervening and is better understood as interlocking or dovetailing, in which the came under the command of the and joined with the defensive garrison and its fortifications. The term was adopted during the Battle of Arras (9 April – 16 May 1917) to replace (relief division), to end confusion over the purpose of divisions held in readiness. There were also calls for each to have the support of an but Ludendorff could not find sufficient divisions for this. James Edmonds, the British official historian, called them special reserve or super counter-attack divisions. Such methods required large numbers of reserve divisions ready to counter-attack, which were obtained by creating divisions, moving some divisions from the eastern front and Operation Alberich () in March 1917, which shortened the front. By the spring, the German army in the west () had accumulated a strategic reserve of Over the winter, certain divisions were trained as but a strict distinction between these divisions and the remaining could not always be maintained.
The new system reflected the views of Carl von Clausewitz that defensive battle should not be passive but one of deflection and attack (""), with the providing a "flashing sword of retaliation" (""). On 1 January 1917, General Otto von Moser was appointed to lead a new at Solesmes near the Belgian border, to teach the new defensive thinking, using a training ground and a Testing and Instructional Division at full establishment for demonstrations. The first course from 8 to 16 February was attended by about of the who attended morning lectures and afternoon exercises and a second course run from 20 to 28 February included guest officers from the Eastern Front and three Austro-Hungarian army observers. The third course from 4 to 12 March included officers from other armies of the Central Powers and then Moser was transferred to take command of the XIV Reserve Corps. Many of the students accepted the new defensive thinking but Loßberg and other dissenters objected to discretion to retreat being given to the front garrison. A second school was set up at Sedan for the officers of . During the British preparatory bombardment of Messines Ridge before the attack on 7 June, the 24th Division was relieved by the 35th Division and the 40th Division by the 3rd Bavarian Division, the local and these were replaced by the 7th Division and the 1st Guard Reserve Division, unfamiliar with the area and not trained . Some were retained as they were rebuilt after spending time in the line; the 24th Division was given six weeks' rest and reconstituted as the of Group Aubers before returning to Flanders on 11 August. The 23rd Reserve Division acted as a from 23 June to 29 July, spent August recuperating and September as an for (Group) Dixmude, before being rushed to Group Ypres on 20 September to relieve the 2nd Guard Division.
Training