What purpose does Hardy serve in the play?

Hardy appears at the start of Act 1 and serves to give information to the audience about the conditions in the trenches that the soldiers would have to endure. It is essential that the audience understand the conditions, not only so that they can follow the play but so that they can see how ill-informed Raleigh is of the conditions. The information he gives is as follows:

Drinking Water "Don't have too much water, it's rather strong today"
Wet Trenches "Guaranteed to keep the feet dry.Trouble is,it gets so wet doing it"

Fighting "Sometimes nothing happens for hours on end; then - all of a sudden - 'over she comes!' - rifle grenades - Minnies - and those horrid little things like Pinapples - you know"

German attack "By the way, you know the big German attack's expected any day now"

Length of stay "Are you here for six days?"

Size of front controlled "We hold about two hundred yards of front line."

Sleeping arrangements "The servants and signallers sleep in there. Two officers in here, and three in there"

Number of rats "I should say - roughly - about two million; but then, of course, I don't see them all. 

Lack of officers " That is, if you've got five officers"

Lack of supplies "Twenty-five right leg and nine left leg"