the 1915 fa cup final would be the last game in england for four years .
so many soldiers in the terraces saw it be known as the khaki cup final .
on friday it will be 100 years since the match was held at old trafford .
sheffield united beat chelsea 3-0 but there was no parade for the victory .
it was played on the same day thousands of allied troops were killed in a deadly german chlorine gas attack near ypres , belgium .
earl of derby urged men not enlisted to play ` a sterner game for england '