Why is the child weeping in peace and future cannon fodder?

it is because above him 1940 class, this cartoon was set in the 1919 so in 1940 there will be another war in which that child be taking part after 21yrs. The cartonist was very accurate with his prediction as in fact WW2 broke out in 1939 so this child would have definately fought and most likely die in the war.