Copied from a genealogical web page:
http://www.barnesfamilync.com/pdf%20files/POEM%20A%20Soldier's%20Alphabet.pdf
where it says this comes from the diary of Octavia Barnes, born 1890, of Wayne County, North Carolina, who kept a diary from 1916 to 1923.
^^
SOLDIER'S ALPHABET

A is for our Army Uncle Sam's best
B is for boys that can stand the test
C is for colors, Red, White, and Blue
D is for duty which we will all do
E is for enemy which we will crush
F is for fight and we are at it in a rush
G is for God, in his power we trust
H is for Huns we will capture or burst
I is for intention which we meant well
J is for Jesus at his mercy we dwell
K is for Kaiser, the big German hound
L is for liberty, in America it abounds
M is for money the amount has no ends
N is for Nature, which we will defend
O is for our boys with grit and nerve
P is for Pershing, the man we are eager to serve
Q is for quickness and we are like a cat
R is for Recruits, eager to be at the bat
S is for Sammie's'a very peculiar name
T is for troops training for the game
U is for Uncle [? barely legible] who is young and gay
V is for Victory we will bring home to stay
W is for war and that's what we are at
X mean xterminate the Huns like a rat
Y is for you to help and don't wait a minute
Z is for Zoo, so let's put Kaiser Bill in it