Service in WW1 - 1914 - 1918 (General)

by ForestPrints , Yorkley, Forest of Dean, UK, Tuesday, November 13, 2012, 07:34 (4396 days ago)

My grandfather who was born in 1878 who was 36 at the opening of WW1, enlisted in 1915 but was not mobilised until July 1917.
He was a carpenter with 566 Wks Coy Royal Engineers.
Why would there have been such a gap between enlistment & mobilisation?