Conditions

The front lines are not only unsafe because of their position but because of the conditions in which the soldiers are living. Sleeping is virtually impossible, the dug-outs are poorly constructed and infested by rats, and the rations are questionable. In addition, the weaponry is in bad shape. The grenades are rusty

Oh, no. (He points to the bed in the right corner.) That's mine. The ones in the other dugout haven’t got any bottoms to them. You keep
yourself in by hanging your arms and legs over the sides. Mustn’t hang your legs too low, or the rats gnaw your boots.

Osborne : You got many rats here ?

Hardy : I should say—roughly—about two million ; but then, of course, I don’t see them all.

___________________________________________________

Here you are : 15 rifle grenades —I shouldn’t use them if I were you ; they upset Jerry and make him offensive. Besides, they are rusty, in any case.

___________________________________________________

Mason : Soup, sir—cutlets—and pineapple.
Osborne {suspiciously) : Cutlets ?

Mason : Well, sir—-well, yes, sir—cutlets.

Osborne : What sort of cudets ?

Mason : Now, sir, you’ve got me. I shouldn’t like to commit meself too deep, sir.

Osborne : Ordinary ration meat ?

Mason : Yes, sir. Ordinary ration meat, but a noo shape, sir. Smells like liver, sir, but it ’asn’t got that smooth, wet look that liver’s got.

at the beginning of the play where hardy and osborne joke about hardy's sock

"guaranteed to keep the feet dry. trouble is, it gets so wet doing it"

this is because the trenches were damp and caused trench foot.