Injured and sent home
On 28th May 1917, when Arthur had been at the front for 2 months, the 294th SB were engaged in a huge bombardment of the German front line at Messines, leading into the battle of messiness, which itself was a crucial preparation for the 3rd Battle of Ypres (Paschendale). The Battery diaries state on 28th May "Warneton retaliation - 2 guns out of action". Warneton is a nearby village. Although there is no hard evidence, Arthur was injured with shrapnel wounds to the chest and abdomen, and received treatment at the Field Hospital at Poperinge where he was assessed to have "S.W (shot wounds?) chest (severe)". By 30th May he had been moved to 3rd Canadian General Hospital at Boulogne and was repatriated on or around 6th June. He was sent to a hospital near Woking (see picture - Arthur is 3rd from left on the front seated row), and spent many moths recovering. He eventually was given a medical discharge on 28th February 1918 and returned home to his wife in Grantham shortly afterwards.
WOC stands for Wounds Ostomy and Continency (nursing) a series of specialisms for patients with abdominal injuries. this link tells you more. http://en.wikipedia.org/wiki/Wound,_ostomy,_and_continence_nursing