Compare the messages in All Quiet on the Western Front to "Soldier's Home."
I think that the fundamental message of each work is how the machinery of war causes profound changes to the soldiers who survive it. In each work, war is perceived by everyone who doesn't fight it as a gloriously Romantic experience. The teachers and adults that encourage the German children to fight in the great war, unaware of or unwilling to accept the dehumanizing reality of war. In Krebs' hometown in Oklahoma, the townspeople crowd him to find out how "great" war is. In both of these, the message of how war is vastly different from how it is perceived is evident.
The message of both works is how war forever transforms the lives of the soldiers who fight. The survivors of war are changed, forced to endure consciousness as an experience where the shadow of war is unshakable. War creates a reality in which there is a forlorn condition which prevents full immersion into life as it was before the dehumanization that is war. In both works, the message is one in which war is not patriotic or triumphant. Rather, war is shown to be an experience that severs bonds between surviving soldiers and the world in which they reenter. The roles in which soldiers are asked to "fit" in a social order is coupled with the reality that returning soldiers are "weary, broken, burnt out, rootless, and without hope." Such an idea becomes the message of each work.