There are records for a James Driscoll in the Royal Irish Rifles who served from about 1898 (just possible to have joined at that age if he fibbed) and who was commissioned after the war. None of the records have anything to confirm his place/date of birth or any other info.
There are many other J Driscolls, none that have Tralee/Kerry linked.
Does his marriage cert have any military detail?
MaxD