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Battle

Cambrai

20 November — 7 December 1917

Surprise opens the line; reinforcement flow lags behind the breach

Military history

Why did combined-arms surprise open the Hindenburg Line while leaving the British gains fragile?

The Cambrai operation begins with an unusual method for the Western Front: tanks, infantry, and predicted artillery fire are concentrated in secret, then the guns open without visible preliminary registration. On 20 November, this combination crosses several systems of the Hindenburg Line. The result, however, is not an open road to Cambrai. Flesquières delays the northern wing, the Masnières bridge and communications slow the cavalry, breakdowns reduce the armored force, and British reserves do not flow through the breach at the expected rate. The decision to press toward Bourlon then deepens a salient that is difficult to supply. From 30 November, German groups concentrate brief fire and assault units against its flanks, especially in the south. The British withdrawal from Bourlon and stabilization on 7 December leave a documented tactical breakthrough, but not the operational decision sought.

Ground chosen for tanks and secrecy

West of Cambrai, the chalky ground is less devastated than Flanders and appears passable for Mark IV tanks. The Hindenburg Line nevertheless includes two trench systems, deep belts of wire, and concrete works. The chosen sector therefore combines an opportunity for mobility with a defense still capable of channeling the advance.

A short raid becomes a territorial operation

The Tank Corps’ initial project is limited; Third Army orders expand the objective to a breakthrough, the crossings at Marcoing and Masnières, Bourlon, and the isolation of Cambrai. The forty-eight-hour limit remains in the plan because strong German reserves are expected to arrive afterward.

The 476 vehicles fall into several categories

The total comprises 378 fighting tanks and 98 support vehicles. The breakthrough also depends on artillery, engineers, infantry, cavalry, and aircraft. Reducing the mechanism to an armored mass erases the predicted barrage, fascines, and infantry work that make the crossings possible.

A surprised defense

The German sector is caught off guard by the time and form of the attack, but its fortifications, machine guns, and batteries do not disappear. At Flesquières, the ridge and reverse-slope fire break the continuity of the advance; at Masnières, the canal and bridge restrict the forces able to exploit the breach.

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Chronological dossier

Battle · 21 February — 15 December 1916VerdunThe German concentration opens the right bank but does not take Verdun; reliefs, artillery and the Sacred Way stabilise both banks, then the October and December offensives recapture Douaumont, Vaux and most of the eastern gains.Battle · 24 October — 12 November 1917CaporettoThree coordinated penetrations through Plezzo, the Isonzo valley and the ridges shatter the IV and XXVII Corps, then the pursuit drives the Italian army back to the Piave.Battle · 8 — 12 August 1918AmiensThe Allies combine tanks, artillery, aviation and infantry to break German defences before they can be rebuilt.Battle · 19 — 25 September 1918MegiddoAllenby pins the Ottomans in the east, breaks through near the coast and sends cavalry into the rear of the Eighth Army.Battle · 26 — 30 August 1914TannenbergThe Germans strip the north, strike Samsonov's two wings separately, then close the roads through Neidenburg, Passenheim and Willenberg around his centre.Battle · 19 February 1915 — 9 January 1916Gallipoli CampaignMines halt the naval gamble; separate landings remain contained below the ridges, then deception enables the evacuation of Anzac, Suvla and Helles.Battle · 1 July — 18 November 1916Battle of the SommeThe bombardment produces opposite results in different sectors; gains in the south and at Bazentin run into strongpoints and reserves, then four months of adaptation push the front back without opening it.Battle · 4 June — 20 September 1916Brusilov OffensiveFour armies prepare several sectors and open the Austro-Hungarian front together; when reserves belatedly concentrate towards Kovel, the Stokhid, German reinforcements and lengthening supply lines exhaust the exploitation.

Military history

Sources

Contemporary primary source, published official dispatchSir Douglas Haig, « The Cambrai Operations », 20 February 1918

§§1–3 « General Plan » pour l’objectif, le terrain, les chars et la limite de 48 heures ; §4 « The Attack of the Third Army » pour le 20 novembre, Flesquières et Masnières ; §5 pour la ligne du 21 novembre ; §§9–14 pour Bourlon et la contre-offensive ; §15 « General Review » pour les attaques convergentes et le repli

The plan attributed to Haig and Byng, surprise, the 48-hour window, initial advance, Masnières bridge, Bourlon, converging attacks, and the British assessment of the result.

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Official institutional military historyDepartment of National Defence, « Cambrai, 1917 »

Champs « Date » et « Context » pour la distinction 20 novembre–3 décembre et 20 novembre–7 décembre ; section « Description », paragraphes 1–4, pour les 300 chars prévus, l’avance du 20 novembre, Masnières, le Fort Garry Horse et la reprise allemande

Official chronology, battle-honour context, the Masnières crossing, the cavalry’s limited action, and the effect of the counterattacks.

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Specialist institutional synthesis, National Army MuseumNational Army Museum, « 1917: Year of Stalemate »

Sections « No breakthrough » §§1–2 pour les pannes et l’absence de réserves ; « Counter-attack » §§1–3 pour le 30 novembre, l’artillerie, le gaz, les storm troops et le repli ; « Lessons » §§1–2 pour les 44 000 et 45 000 et la portée interarmes

Synthesis of the slowdown, problems with reserves and communications, the counteroffensive, and casualty estimates.

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Departmental archive, specialist historical synthesisArchives départementales du Pas-de-Calais, « La bataille de Bourlon »

§§1–3 pour la percée du 20 novembre et l’importance de la crête ; §4 pour l’assaut du 23 novembre et l’attrition des chars ; §§5–7 pour la contre-offensive du 30 novembre, les axes sud et nord, le retrait du 3 décembre et la ligne du 7 décembre

Relational topography of Bourlon, chronology of the fighting, asymmetry of the counteroffensive, territorial outcome, and published casualty ranges.

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Specialist military-history synthesisThe Long, Long Trail, « The Cambrai operations, 1917 »

§§ « The plan » et « Operation GY » pour le front de 10 000 yards et le passage de la cavalerie ; « Dawning of a new era » pour le tir calculé et les 476 chars ; « Tank attack, 20–21 November » pour Flesquières, Masnières et les 179 engins hors d’action ; « Capture of Bourlon Wood » et « German counter attack » pour les phases suivantes

Specialist reconstruction of objectives, divisions, progress, crossings, Bourlon, and the counteroffensive; used for comparison. Treating it as the sole casualty authority would exceed its documentary role here.

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Institutional military-history study, Army University PressArmy University Press, Lethal and Non-Lethal Fires, vol. 3, « Cambrai: The Evolution of British Field Artillery Tactics »

PDF pp. 41–45 pour le choix du terrain, la préparation, le plan et la limite de 48 heures ; figure 2.2 p. 44 pour le dispositif ; pp. 51–55 pour les 1 003 pièces, l’horaire du 20 novembre, les 378 chars de combat et les 179 hors d’action

The mechanism of predicted fire, artillery assets, distribution of tanks, the first day, and material causes of the slowdown.

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Specialist academic military monographMatthew R. Prescott, Failing to Exploit Success: The British Army at Cambrai

Résumé et introduction pp. 4–9 ; plan et ordre de bataille pp. 13–17 ; récit de l’action pp. 18–30 ; analyse de l’exploitation, du commandement et de la contre-offensive pp. 31–45 ; tableau des pertes p. 36

Criticism of the shift from raid to operation, order of battle, inadequate reserves and communications, maps of the counteroffensive, and the high estimate of German casualties.

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Institutional entry from a German historical museumDeutsches Historisches Museum, « Die Schlacht bei Cambrai 1917 »

LeMO, paragraphes « Im Zuge der Offensive » et « Die Briten hatten » pour la ligne Siegfried, les 378 chars de combat et 98 engins de soutien, la surprise sans Trommelfeuer et le faible changement final du front

Cross-checking from the German institutional perspective, breakdown of the armored fleet, and bounds of the territorial outcome.

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Institutional map, United States Military AcademyUSMA, Map 17, « The Battle of Cambrai »

Panneau « The Battle of Cambrai » : front du 20 novembre, limite de l’avance britannique, contre-offensive allemande et ligne finale autour de Moeuvres, Bourlon, Flesquières, Marcoing, Gonnelieu et Vendhuille

Northwest–southeast orientation, relationships among the Hindenburg Line, Bourlon, Flesquières, Masnières, Gouzeaucourt, and Cambrai, and checks on the initial and final lines.

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Local institutional source, municipality of MasnièresPatrimoine — Masnières

Sections « Le canal de Saint-Quentin » et « Masnières, village incontournable de la Bataille de Cambrai » pour le franchissement du 20 novembre 1917, le pont fragilisé par une explosion et la limite nord-est de l’avance britannique

Cross-checking the canal’s name and the role of the Masnières bridge in constraining exploitation.

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Edited by BattlesInMotion.com