I caught this cartoon on TCM a few days ago. It was created in 1939 by Hugh Harman on the eve of WWII. Squirrels ask their grandfather after singing Christmas Carols invoking "Peace on earth, good will to men," what men are. Apparently, there are no more men on earth. They've annihilated themselves. Quite graphic. Luckily animals survived the holocaust. And the Bible.
See also the 1960's remake titled, "Good Will To Men" by Hanna and Barbera here.