I never thought of this as a military song, but Sandburg did. To me, it was a kids' camp song.

THE HEARSE SONG
Casualty records of the world war indicated in round numbers ten million dead and twenty million crippled. The Hearse Song was popular in all branches of service, though in the aviation corps it had more variants. The version (A) is from James Stevens, Irma H. Thrane and W. W. Woodbridge of Washington, while (B) is from Jake Zeitlin of Los Angeles and Fort Worth.

THE HEARSE SONG (Sandburg - A)

1. The old Grey Hearse goes rolling by,
You don’t know whether to laugh or cry;
For you know some day it’ll get you too,
And the hearse’s next load may consist of—you.

2. They’ll take you out and they’ll lower you down,
While men with shovels stand all a-round;
They’ll throw in dirt and they’ll throw in rocks,
And they won’t give a dam-m-m if they break the box.

3. The worms crawl in and the worms crawl out,
They crawl all over your chin and mouth,
They invite their friends and their friends’ friends too,
And you look like hell when they’re—through—with you.

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THE HEARSE SONG (Sandburg - B)

Did you ever think as the hearse rolls by
That some of these days you must surely die?
They’ll take you away in a big black hack,
They’ll take you away but won’t bring you back.

The men with shovels stand all around.
They shovel you into that cold, wet ground.
They shovel in dirt and they throw in rocks.
They don’t give a dam if they break the box.

And your eyes drop out and your teeth fall in
And the worms crawl over your mouth and chin;
And the worms crawl out and the worms crawl in
And your limbs drop off of you limb by limb.

Source: Carl Sandburg's American Songbag, page 444 (Harcourt, Brace, & World, 1928)