The men pictured were Tyneside Scottish Northumberland Fusiliers during a practice operation at Rothbury Racecourse in 1916.
The specialists were then given the task of tunnelling under the trenches at the River Somme so the Allied forces could attack German forces from behind.
However, they were said to have all blown up during the operation.
The picture is a treasured one for Morpeth resident Lindsay Taylor and other family members as his grandfather Corporal Emanuel Joseph Taylor, known as Mattie Taylor, is in the middle of the front row. Mr Taylor said the majority of the men would have been in their late teens or early 20s.