Harkening back to the old U.S. Army Signal Corps days, here's an old mildewed book I have that Sgt. George Baker, creator of The Sad Sack, personalized (above) to my dad. I don't know if Baker was technically in the animation unit, but then again, when it came to creatives -- no mattter what their particular facility -- every cartoonist (using that term in general) knew each other.
Rather than send you to Wiki's blurb on Sad Sack, let's just let the book do the talking.
Books in wartime, Egad!:
The Introduction: You might want to read the whole thing, but I'll paraphrase that Sad Sack first appeared in Yank magazine in 1942. "The Sack is Army's perfect personification of the Army's little man, the hopeless underdog who has no stripes, no glory, no friends in the orderly room, no escape from the dread terror of red tape and higher ranks. Since he is the Army's little man, none of his problems are of his own making. No matter what he does or leaves undone, trouble will come to him from outside forces. "
The deal, storywise, with Sad Sack, is that no matter how hard he tries, he always gets the crap end of the military pecking-order stick: the end gag is always the same...he's just a sad sack of... The book is flush with pages -- those scanned below are, to my own eyes, representative of what you would find.