Question: In which month of 1917 did this battle during the World War I, in which Henry Maitland Wilson participated, start?

Context paragraphs:
20th Infantry Division (Greece): The 20th Infantry Division (Greek: 20ή Μεραρχία Πεζικού ) was a short-lived formation of the Hellenic Army.  It was founded on 24 January 1941, when Grece was already embroiled in the Greco-Italian War.  Formed of reservists and with an incomplete table of equipment, it was assigned to the Central Macedonia Army Section (TSKM), forming part of the Greek–British "W Force", under the British Lt. General Henry Maitland Wilson.  The division opposed the German invasion of Greece, but was defeated and practically ceased to exist as a combat formation at the Battle of Kleisoura Pass on 13–14 April.

HMS Tiger (1913): HMS "Tiger" was a battlecruiser of the Royal Navy and the eleventh ship to bear that name.  She was built by John Brown and Company of Clydebank, Scotland, and launched in 1913.  "Tiger" was the most heavily armoured battlecruiser of the Royal Navy at the start of the First World War, but was not yet ready for service.  The ship was assigned to the 1st Battlecruiser Squadron (1st BCS) for the duration of the war and participated in the Battle of Dogger Bank in early 1915, though she was still shaking down and did not perform well.  "Tiger" next participated in the Battle of Jutland in 1916, where she was only lightly damaged despite suffering many hits by German shells.  Apart from providing distant cover during the Second Battle of Heligoland Bight in 1917, she spent the rest of the war on uneventful patrols in the North Sea.

Armistice of Saint Jean d'Acre: The Armistice of Saint Jean d'Acre (also known as the Convention of Acre) concluded the Syria-Lebanon Campaign of World War II.  The Armistice, signed on 14 July 1941, was between Allied forces in the Middle East under the command of British General Henry Maitland Wilson, and Vichy France forces in Syria and Lebanon, under the command of General Henri Dentz, Commander in Chief of the Army of the Levant ("Armée du Levant") and as High Commissioner of the Levant.

Henry Maitland Wilson: Field Marshal Henry Maitland Wilson, 1st Baron Wilson, (5 September 1881 – 31 December 1964), also known as Jumbo Wilson, was a senior British Army officer of the 20th century.  He saw active service in the Second Boer War and then during the First World War on the Somme and at Passchendaele.  During the Second World War he served as General Officer Commanding-in-Chief (GOC-in-C) British Troops in Egypt, in which role he launched Operation Compass, attacking Italian forces with considerable success, in December 1940.  He went on to be Military Governor of Cyrenaica in February 1941, commanding a Commonwealth expeditionary force to Greece in April 1941 and General Officer Commanding (GOC) British Forces in Palestine and Trans-Jordan in May 1941.

Central Macedonia Army Section: The Central Macedonia Army Section (Greek: Τμήμα Στρατιάς Κεντρικής Μακεδονίας, ΤΣΚΜ , "Tmima Stratias Kentrikis Makedonias", "TSKM") was an army corps-level command of the Hellenic Army established on 6 March 1941.  It was commanded by Lt. General Ioannis Kotoulas and comprised the 12th Infantry Division and the 20th Infantry Division.  On 28 March it was assigned to Henry Maitland Wilson's 'W' Force, holding the Vermion Mountains–Haliacmon line.  It was defeated and dissolved in mid-April 1941 during the German invasion of Greece.

Baron Wilson: Baron Wilson, of Libya and of Stowlangtoft in the County of Suffolk, was a title in the Peerage of the United Kingdom.  It was created in 1946 for the prominent military commander Field Marshal Sir Henry Maitland Wilson.  The title became extinct on the death of his only son, the second Baron, in 2009.

Henry Fuller Maitland Wilson: Lieutenant-General Sir Henry Fuller Maitland Wilson, KCB, KCMG, (18 February 1859 – 16 November 1941) was a British soldier who served in the Second Anglo-Afghan War, the Second Boer War and the First World War, during which he commanded a division on the Western Front and an army corps at Salonika.

Baron Wilson (disambiguation): Baron Wilson is a title created in 1946 for Sir Henry Maitland Wilson.

Battle of Passchendaele: The Battle of Passchendaele (German: "Flandernschlacht" , French: "Deuxième Bataille des Flandres" ), also known as the Third Battle of Ypres, was a campaign of the First World War, fought by the Allies against the German Empire.  The battle took place on the Western Front, from July to November 1917, for control of the ridges south and east of the Belgian city of Ypres in West Flanders, as part of a strategy decided by the Allies at conferences in November 1916 and May 1917.  Passchendaele lay on the last ridge east of Ypres, 5 mi from a railway junction at Roulers, which was vital to the supply system of the German 4th Army.  The next stage of the Allied plan was an advance to Thourout–Couckelaere, to close the German-controlled railway running through Roulers and Thourout.

Oasis (anthology): Oasis was a literary anthology published in Cairo during World War II.  It was edited by Denis Saunders, David Burk, and Victor Selwyn.  The introduction was written by General Henry Maitland Wilson, who was at this time Commander-in-Chief of the Middle East.

Supporting paragraphs: Henry Maitland Wilson Battle of Passchendaele
Answer: July