From "John Brown's Body" by Stephen Vincent Benét, via a MT forum link in Mark Horstmann's "Things I Think I Think" mailing list. The complete poem can be found here. Mark, meanwhile, was alluding to the poem because of this New Yorker cartoon.
If you take a flat map And move wooden blocks upon it strategically, The thing looks well, the blocks behave as they should. The science of war is moving live men like blocks. And getting the blocks into place at a fixed moment. But it takes time to mold your men into blocks And flat maps turn into country where creeks and gullies Hamper your wooden squares. They stick in the brush, They are tired and rest, they straggle after ripe blackberries, And you cannot lift them up in your hand and move them. — A string of blocks curling smoothly around the left Of another string of blocks and crunching it up — It is all so clear in the maps, so clear in the mind, But the orders are slow, the men in the blocks are slow To move, when they start they take too long on the way — The General loses his stars, and the block-men die In unstrategic defiance of martial law Because still used to just being men, not block-parts.
And yet another fragment of the poem dealing with wooden blocks, more grim and more determined.
That is the chess and the scheme of the wooden blocks Set down on the contour map. Having learned so much, Forget it now, while the ripple-lines of the map Arise into bouldered ridges, tree-grown, bird-visited, Where the gnats buzz, and the wren builds a hollow nest And the rocks are grey in the sun and black in the rain, And the jacks-in-the-pulpit grow in the cool, damp hollows. See no names of leaders painted upon the blocks Such as "Hill," or "Hancock," or "Pender" — but see instead Three miles of living men — three long double miles Of men and guns and horses and fires and wagons, Teamsters, surgeons, generals, orderlies, A hundred and sixty thousand living men Asleep or eating or thinking or writing brief Notes in the thought of death, shooting dice or swearing, Groaning in hospital wagons, standing guard While the slow stars walk through heaven in silver mail, Hearing a stream or a joke or a horse cropping grass Or hearing nothing, being too tired to hear. All night till the round sun comes and the morning breaks, Three double miles of live men. Listen to them, their breath goes up through the night In a great chord of life, in the sighing murmur Of wind-stirred wheat. A hundred and sixty thousand Breathing men, at night, on two hostile ridges set down.