From the recording Pack Up Your Troubles notes & lyrics
The chorus is well-known, and for good reason. I actually do not much care for the lyric to this song, except in its ability to show the absolute callousness of arm-chair warriors. There is something about the gung-ho attitude of good old Private Perks that tends to curdle the blood. The chorus is quintessential World War I, though, and was sung by the troops, I'm sure with plenty of irony.