Question: What unofficial ceasefires along the Western Front of World War I were described by Sir Edward Hulse in letters published posthumously?

Context paragraphs:
Canadian Expeditionary Force: The Canadian Expeditionary Force (CEF) was the designation of the field force created by Canada for service overseas in the First World War.  The force fielded several combat formations on the Western Front in France and Belgium, the largest of which was the Canadian Corps, consisting of four divisions.  The Canadian Cavalry Brigade and the Canadian Independent Force, which were independent of the Canadian Corps, also fought on the Western Front.  The CEF also had a large reserve and training organization in England, and a recruiting organization in Canada.  In the later stages of the European war, particularly after their success at Vimy Ridge and Passchendaele, the Canadian Corps was regarded by friend and foe alike as the most effective Allied military formation on the Western Front.  The Germans went so far as to call them "storm troopers" for their great combat efficiency.  In August 1918, the CEF's Canadian Siberian Expeditionary Force travelled to revolution-torn Russia.  It reinforced an anti-Bolshevik garrison in Vladivostok during the winter of 1918–19.  At this time, another force of Canadian soldiers were placed in Archangel, where they fought against Bolsheviks.

Western Front (Russian Empire): The Western Front (Russian: Западный фронт ) was an army group in the armed forces of the Russian Empire during the First World War.  It was established in August 1915 when the Northwestern Front was split into the Northern Front and Western Front, and was disbanded in 1918.  From the time of its formation until the final year of its existence, the Western Front's field headquarters was in Smolensk, but it was later moved to Minsk.

Edward Fanshawe (British Army officer): Lieutenant-General Sir Edward Arthur Fanshawe KCB (4 April 1859 – 13 November 1952) was a British Army general of the First World War, who commanded the 11th (Northern) Division at Gallipoli and the V Corps on the Western Front during the Battle of the Somme, the Third Battle of Ypres, and the 1918 Spring Offensive.  He was the second eldest of four brothers Henry Leighton Fanshawe, the eldest, (Edward), Hew, and Robert) and he, together with the last two, all rose to command divisions or corps during the war.

Sir Edward Hulse, 7th Baronet: Sir Edward Hamilton Westrow Hulse, 7th Baronet (31 August 1889 – 12 March 1915) was an officer in the British Army during the First World War.  He had his letters published posthumously detailing his account of the fighting on the Western Front, describing events such as the Christmas Truce.

Bermudians in the Canadian Expeditionary Force: Many British nationals from the United Kingdom or colonies who were resident in Canada during the First World War joined the Canadian Expeditionary Force, which was deployed to the Western Front.  A sizeable percentage of Bermuda's volunteers who served in the war joined the CEF or the Royal Canadian Navy (RCN), either because they were resident in Canada already, or because Canada was the easiest other part of the British Empire and Commonwealth to reach from Bermuda (1,239 kilometres (770 miles) from Nova Scotia).  As several CEF battalions were posted to the Bermuda Garrison before proceeding to France, islanders were also able to enlist there.  Although the Bermuda Militia Artillery (BMA) and Bermuda Volunteer Rifle Corps (BVRC) both sent contingents to the Western Front, the first would not arrive there until June 1915.  By then, many Bermudians had already been serving on the Western Front in the CEF for months.  No further contingents were sent to France by the BVRC after 1916, however forty-seven BVRC NCOs and Riflemen (Privates) were permitted to re-enlist in Canada during the course of the war.  Although some enlisted in British Army organs in Canada, including the Royal Flying Corps, most joined the Canadian Expeditionary Force.  Bermudians in the CEF enlisted under the same terms as Canadians.

Edward Northey (British Army officer): Major General Sir Edward Northey (May 1868 – December 1953) was a senior British Army officer of the First World War who commanded a brigade on the Western Front until wounded in 1915.  Returning to service in 1916, Northey took command of a colonial force in Nyasaland in the East African Campaign, later becoming Governor of Kenya.  He later served as a general of Territorial forces and retired in 1926.

Sir William Robertson, 1st Baronet: Field Marshal Sir William Robert Robertson, 1st Baronet, (29 January 1860 – 12 February 1933) was a British Army officer who served as Chief of the Imperial General Staff (CIGS) – the professional head of the British Army – from 1916 to 1918 during the First World War.  As CIGS he was committed to a Western Front strategy focusing on Germany and was against what he saw as peripheral operations on other fronts.  While CIGS, Robertson had increasingly poor relations with David Lloyd George, Secretary of State for War and then Prime Minister, and threatened resignation at Lloyd George's attempt to subordinate the British forces to the French Commander-in-Chief, Robert Nivelle.  In 1917 Robertson supported the continuation of the Third Ypres Offensive, at odds with Lloyd George's view that Britain's war effort ought to be focused on the other theatres until the arrival of sufficient US troops on the Western Front.

Richard Levett: Sir Richard Levett (also spelled Richard Levet) (died 1711), Sheriff, Alderman and Lord Mayor of London, was one of the first directors of the Bank of England, an adventurer with the London East India Company and the proprietor of the trading firm Sir Richard Levett & Company.  He had homes at Kew and in London's Cripplegate, close by the Haberdashers Hall.  A pioneering British merchant and politician, he counted among his friends and acquaintances Samuel Pepys, Robert Blackborne, John Houblon, physician to the Royal Family and son-in-law Sir Edward Hulse, Lord Mayor Sir William Gore, his brother-in-law Chief Justice Sir John Holt, Robert Hooke, Sir Owen Buckingham, Sir Charles Eyre and others.

Attack on the Gommecourt Salient: The Attack on the Gommecourt Salient was a British operation against the northern flank of the German 2nd Army that took place on 1 July 1916, on the Western Front in France, during the First World War.  The attack was conducted by the British Third Army (Lieutenant-General Edmund Allenby) as a diversion, to protect the northern flank of the main attack by the British Fourth Army on the First day on the Somme, from Serre southwards to the boundary with the French Sixth Army at Maricourt.  To extend the attack front of the Fourth Army, the VII Corps (Lieutenant-General Thomas Snow) of the Third Army was to capture the Gommecourt Salient, the most westerly point of the Western Front.  In the first week of May, the 56th (1/1st London) Division (Major-General Charles Hull) and the 46th (North Midland) Division (Major-General Edward Montagu-Stuart-Wortley) moved into the area for the attack.  By 10 May, both divisions had taken over the front on the right flank of the 37th Division (Major-General A. Edward W. Count Gleichen) and begun training for the operation, making no attempt to conceal the preparations.

Christmas truce: The Christmas truce (German: "Weihnachtsfrieden" ; French: "Trêve de Noël" ) refers to a series of widespread but unofficial ceasefires along the Western Front of World War I around Christmas 1914.

Supporting paragraphs: Sir Edward Hulse, 7th Baronet Christmas truce
Answer: The Christmas truce