First World War
Following the unexpected death of Lieutenant General Sir James Grierson on his arrival in France in 1914, Plumer was considered for command of one of the two corps which made up the British Expeditionary Force (BEF) alongside the GOC I Corps, commanded by Lieutenant General Sir Douglas Haig: this position eventually went to General Sir Horace Smith-Dorrien instead. Plumer was sent to France in February 1915 and given command of V Corps which he led at the Second Battle of Ypres in April 1915.
He succeeded Smith-Dorrien in command of the Second Army of the BEF in May and, having been promoted to full general on 11 June 1915, and was in command of the Army during the Actions of St Eloi Craters. He won an overwhelming victory over the Imperial German Army at the Battle of Messines in June 1917.
The battle started with the simultaneous explosion of a series of mines placed by the Royal Engineers' tunnelling companies beneath German lines. The detonation created 19 large craters and was described as the loudest explosion in human history. After the mines were fired, Plumer's men left their trenches and advanced 3,000 yards. He won further victories at the Battle of the Menin Road Ridge and the Battle of Polygon Wood in September 1917 and the Battle of Broodseinde in October 1917 advancing another 5,000 yards in the process.
In November Plumer, who in August had been made colonel of the York and Lancaster Regiment, gave up control of the Second Army when he was given command of the Italian Expeditionary Force, which ultimately grew into a force of five British divisions withdrawn from the West, sent to the Italian Front after the disaster at Caporetto.
Early in 1918, Plumer was sought by Prime Minister David Lloyd George for the position of Chief of the Imperial General Staff as a replacement for General Sir William Robertson: he declined the position.
Plumer instead returned to the Western Front and resumed command of the Second Army, which soon found itself involved in the German spring offensives which began in March 1918. Plumer's Second Army "was driven back from Messines, Wytschaete and Passchendaele, but, in a determined resistance, held on to Ypres".
In September, after the Allies counterattacked the Germans at the Second Battle of the Marne, and during the Hundred Days Offensive which followed, the Supreme Allied Commander on the Western Front, Ferdinand Foch, "placed Plumer and the Second Army under command of King Albert I of the Belgians", which formed part of the Flanders Group of Armies and which "made extensive gains" before the Armistice of 11 November 1918 finally brought the war to an end.
