Here from the Streatham and Croydon Rugby Club (Icons passim) is a quote to give us pause:
No matches were played during the First World War from 1914-18. With the cessation of hostilities in WW1 , in which thirty three members - one third of the membership in 1914 - gave their lives, those fortunate enough to return were eager to restart the club and play rugby again.
One third of the membership. Scale that up over a country, a continent, a world.