|Private Pyle is not enjoying basic training.|
Stress levels in this situation are high. Basic training is tough, there are obstacles to overcome (actual towering wooden contraptions that poor Private Pyle can't navigate). At the same time, Hartman is trying to merge man and gun through endless drill marching that features cadence calls in which the soldiers sing about their rifles while grabbing their crotches. Later, the rifle becomes a girlfriend to the men, when Hartman demands they give their rifles a girl's name and sleep with them in their bunks. All this activity is supposed to make these men into soldiers- to make them forget who they used to be. Indeed, Pyle gets in a lot of trouble when he makes a mistake during a march. Hartman immediately accuses him of trying to be "different." To become a soldier, difference and individuality must be eliminated. There is very little freedom in the soldier's identity- especially during the time of the draft when half the men serving weren't there because they wanted to be, but rather because they were forced.
All this training does make some of the privates into good soldiers and it drives others insane. Kubrick seems to be saying something about the fragile nature of masculinity-- attempt to create it with too much force and violence and it will self-destruct.
Reeser, Todd W., Masculinities in Theory.