On the outbreak of war in 1914, Maurice was posted to France and assigned to Major General
Hubert Hamilton's
3rd Division as its general staff officer, grade 1, or
chief of staff, in late August. and saw action at the
Battle of Mons. and brevet colonel in June 1915. In 1915 Maurice, who in February was made a CB, was director of military operations at GHQ (later handing over to
"Tavish" Davidson). He wrote papers for the BEF Chief of Staff William Robertson and the Commander-in-Chief Sir John French. Maurice stressed that the high troops-space ratio was the main cause of the stalemate on the Western Front, an argument which he would later repeat in his book
British Strategy (1929). Because the defender could bring up reinforcements quicker than the attacker could feed in fresh units and move his guns forward, no breakthrough was likely to be achieved without a long preceding (battle of attrition) elsewhere. Maurice argued that the two types of battle were very different. The former aimed at breaking through to open country even if launched from tactically unfavourable ground, preferably over a wide breach to lessen enemy
enfilade fire from the flanks. By contrast a should be a series of battles (at least every ten days, as it took the Germans three weeks to bring fresh units from Germany) over ground where the defender had to stand and counter-attack, thus reversing the normal advantage enjoyed by defenders. Good artillery observation and communications (to allow reinforcements of men and shells) were required, not least as the enemy would be retreating towards his own bases whilst the attacker advanced over ground devastated by bombardment. Maurice also argued that the British would not have to the resources to conduct until 1917 but that the French must do so until then, and that the
Battle of Loos in autumn 1915 was a regrettable waste of resources forced on Britain by the need to cooperate with her French senior partner. Maurice was strongly critical of proposals to launch a major offensive out of the Ypres Salient (such plans would be discussed for two years before eventually resulting in the 1917
Battle of Passchendaele). He argued that the Ypres Salient, besides being overlooked by enemy artillery, offered few geographical advantages to the attacker. He conceded that an offensive in this sector might lead to the liberation of the ports of Ostend and Zeebrugge provided it coincided with a major French offensive further south. However, unless the Germans withdrew from Belgium entirely, the British would most likely be left holding a longer line stretching to the Dutch frontier, served by two single-track railways from Dunkirk and Hazebrouck-Ypres-Roulers, while the German positions were served by six double-track rail lines. The Belgian Army, currently protected by the coastal inundations of the River Yser, would be able to offer little assistance and would be left holding positions on the new front line which lacked the benefit of such inundations. Maurice recommended that the Ypres Salient itself should either be extended as far as the high ground of Passchendaele Ridge having first taken the ridges south of the city (this is essentially what would happen in 1917), or else (his preferred option) the line should be shortened by a tactical retreat nearer the city. After Maurice's departure for the War Office, his former staff at GHQ continued to produce papers for his successor "Tavish" Davidson, pointing out that the BEF had never fought a pure battle of attrition but had rather, both at Loos and the Somme, been attempting to achieve breakthrough and attrition more or less simultaneously; disputes continued to simmer during the planning of the
Battle of Passchendaele with both Rawlinson and Plumer producing plans too cautious for
Haig's liking. In 1915 Maurice, who in June was promoted to brevet colonel, was posted to London as Director of Military Operations for the
Imperial General Staff, and in 1916 he was promoted to
major general. Maurice worked closely with
William Robertson, who was appointed
Chief of the Imperial General Staff at the end of 1915, ghostwriting many papers which went out over Robertson's signature. One of Maurice's daughters, Nancy, was the long-term secretary and mistress of
Edward Spears, eventually marrying him in 1969 after the death of his first wife
Mary Borden. Spears later wrote of Maurice in
Prelude to Victory "As imperturbable as a fish, always unruffled ... a rather abrupt manner. A little distrait owing to great inner concentration, he simply demolished work, never forgot anything ... [a] most efficient if not outwardly brilliant second. No man ever wasted fewer words nor expressed himself when he spoke with greater clarity and conciseness". ==Resignation==