Land War: face to face

Wars of 100 years ago were held face to face, rival camps stood waiting while the messages are threatening the most painful punishment if they will not surrender unconditionally.
And usual, there WAS no unconditionally surrender, so the war began.
Frontline soldiers fell first, anyway, what chance would have had a front-line soldier? 1 to 1 million, 1 to 10 million?
So we conclude that the soldiers went to war without hope of returning home. But what lead them to go to a war that will cost lives?
Probably being forced, if he had refused their families suffer. or
were promised treasure,case in which by a miracle will returning home will be rich. Or were disgusted by poverty and needs and preferred to die.