First World War
Peyton returned to England in 1914 on the outbreak of the First World War and took up a new post as GSO1 of the 1st Mounted Division, a Territorial Force (TF) formation. Promoted to major general in 1914 (first as temporary promotion, from October as substantive rank), he became general officer commanding (GOC) of the 2nd Mounted Division, another TF formation, which he led in the Gallipoli campaign, seeing action in August 1915 and later taking part in the final evacuation of Allied forces from Gallipoli on 19 December 1915. The division suffered severe casualties at Suvla in particular.
Peyton then commanded the Western Frontier Force in Egypt in 1916, leading an expedition against the Senussi and re-occupying Sidi Barrani and Sollum, again being mentioned in despatches. For rescuing the shipwrecked British prisoners of HMS Tara from Bir Hakkim (by a force of armoured cars led by Hugh Grosvenor, 2nd Duke of Westminster) he received the special thanks of the Admiralty and was again mentioned in despatches.
In May 1916, after success as a combat commander, Peyton was transferred to the Western Front to become the military secretary to General Sir Douglas Haig remaining with Haig, commander-in-chief (C-in-C) of the British Expeditionary Force (BEF) on the Western Front, until March 1918. The post was at the heart of the operation of the management of appointments, promotions, removals, honours and awards of the BEF. In December of that year he was granted the colonelcy of the 15th The King's Hussars, holding the position until their merger with the 19th Hussars in 1922, and thereafter the colonelcy of the combined 15th/19th Hussars until his death.
Peyton was knighted in 1917, being made a Knight Commander of the Royal Victorian Order when King George V visited the troops in the field.
In April and May 1918, as the German Spring Offensives were underway, Peyton nominally commanded the Reserve Army of the BEF. The Fifth Army had been defeated on the Somme in March 1918 and taken over by the Fourth Army, and the former Fifth Army staff formed a reserve HQ at Crécy-en-Ponthieu. On 23 May, the Fifth Army was reconstituted and given to General Sir William Birdwood, and for six weeks (as a temporary lieutenant general) Peyton took command of X Corps, though his corps was held back from the fighting.
However, from 4 July 1918, when he gave up his temporary rank, until March 1919, he returned to active service as GOC of the 40th Infantry Division, taking over from Major General John Ponsonby. He led the 40th, one of the most junior of the Kitchener's Army divisions, during operations in France and Belgium, leading it through the Hundred Days advance through Flanders until after the Armistice of 11 November 1918.
Peyton's feelings about his postings between May 1916 and July 1918 were expressed silently by his omitting any mention of them from his entry in Who's Who.
