From Indiana University Sheet Music Collections:

WE'RE IN THE ARMY NOW
"Sung by Every Soldier in the United States"
Words, Tell Taylor & Ole Olsen. Music, Isham Jones. 1917.

1. From the looks of things, we've got to join the army.
Uncle Sammy means to do just what he says.
It won't be long before we're in the trenches,
A-fighting for the dear old USA,
So when anything goes wrong,
We'll sing this little song:

CHORUS:
We're in the army now.
We're not behind a plow.
We'll never get rich a-diggin' a ditch. *
We're in the army now.
We're in the army now.
Suppose you wonder how.
But don't you fear. You'll soon be here. *
We're in the army now.

2. Now you see the boys as they go marching by you,
In their uniforms and colors, they look grand.
To the tune of "Yankee Doodle he's a dandy,"
They're marching for the dear old Yankee land.
So when anything goes wrong,
We'll sing this little song: CHORUS

Extra Choruses:

[*Substitute these lines for the ones marked with asterisks above:]

2. We're glad we're here; that's why we cheer.
We'll fight for right with all our might.

3. The time has come to make things hum.
So come along and join our song.

4. A loyal heart can do his part
The world will know and we can show

5. The U-boat war has gone too far.
We'll do what's right. Of course we'll fight.

6. We'll eat pork and beans with appetites keen.
The grub is fair. Why should we care?

7. We'll do our share no matter where.
Our USA needs us today.

8. The time has come to make things hum.
We're going in to fight like sin.

9. We could sing all night. That wouldn't be right.
We're losin' our pipes for the Stars and Stripes.