Future War Tank (1939)
This image appeared on the back cover of the December, 1939 issue of Amazing Stories. The accompanying text for this "Future War Tank" is below.
Future War Tank
This Land Battleship Can Form The Spearhead of Attack in Future Wars
It will be used to penetrate and smash strategic enemy positions and hold them until support arrives. massively armored, they will brush aside ordinary tanks. Only direct hits by heavy guns will affect it. Its anti-aircraft guns will repel aerial attack. Flame throwers will demoralize infantry resistance. Trenches and fortifications will be crumbled. Its crew will defend captured positions for days if need be. Its great weight will pave a road for following infantry and field artillery. Its guns will cover their advance.
You can read more about the history (of the future) of war right here.