Private Dempster arrived in France in September 1915 and fought at the St Eloi Craters in April 1916. He received a gunshot wound in the leg 13 June 1916 during the final days of fighting at Mount Sorrel and spent over a month in hospital. He then moved with his unit to the Somme where he was promoted to sergeant less than a week before his death. Promotions often occurred quickly because of the high casualty rate amongst those who led the infantry platoons into battle, the sergeants and junior officers. Of the fewer than 700 men in Sergeant Dempster's unit who began the attack early on 15 September, within a few hours 405 had been killed or wounded.

Sergeant William Dempster's brother Hugh wrote their mother on 17 September 1916:

"Dear Mother-

Just a line to let you know that I am fine and dandy, but have some very bad news for news for you. Willie got hit by a shell, and I heard of it, so went to see him on the 17th, and it was quite true, for he had died and was buried, so I went to where he was buried and got his kit bag and saw him, and, dear mother, he died with a smile on his face. He was a hero and a soldier. What few of his platoon were left told me that he was the best sergeant they ever had, and was leading his men like a soldier should do. I don't forget, mother, that it is very hard for you at home. I saw Willie on the evening of the 10th, and was with him a long time. They went in the trenches on the llth.

Well, mother, I don't know how poor Alice takes it, for it was very hard for me to see my own brother dead on the battlefield of the Somme, but better than all, his old chum told me that very few soldiers could handle a rifle and a bayonet like he could. His poor chum feels very bad for they were always together. It is pretty hard when it comes to one of our own, too, but before the battle was over, there were thousands of dead lying on the battlefield. I can see them every day by the hundreds. Well, dear mother, I hope you won't take it too hard, or the rest of the family and poor Alice, for I had something to take when I saw him. I tell you, mother, he was fighting for his King and Country, and for dear old Canada, he was fighting to protect wives, mothers, fathers and children from the rule of those Infernal Germans.

I know it will be a consolation to you to know that Willie lived a good life. He went to church every time he could and told me he went to Communion, so I am sure that anyone who dies a hero, not a coward, their place is right in heaven, for you know the Lord hates a coward. He was with his men till they nearly got the third line of German trenches; they had taken two lines, the first and second, and captured several hundred prisoners.

Well, dear mother, I got his barber clippers, comb, pipe, belt, one of his crucifixes, cap, badge, two little buttons, hat, shoulder badge, and numbers, housewife, needles, thread, some of his instruction books, two little wallets, and a few little bronzed leaves that he had got from some church that was shelled to pieces, and I will send them to you, so you can give them to Alice; give all of them some little thing. His chum told me the priest was there. I haven't seen the priest yet, but am going to.

The Battalion lost nearly all the officers they had. Well, dear mother, I will close for this time, hoping to hear from you soon. I remain, your son,"

HUGH DEMPSTER

The fighting from 15 to 22 September forced the Germans back almost a kilometre, a major achievement by Great War standards, but at the cost of 7,230 Canadians killed or wounded. The centre of the attack now is marked by a memorial made of Canadian granite located near the village of Courcelette.

Sergeant Dempster is commemorated on Page 76 of the First World War Book of Remembrance but has no known grave. His name is inscribed on the V1MY MEMORIAL along with the names of 12 other Gananoque men who died in France but whose bodies were never recovered or identified.