i couldnt catch on to one lesson being taught in Marine boot camp. we were in

[leatherneck]

field training during second.... phase, a drill instructor repeatedly threw a recruit's helmet over a small fence and had the recruit repeatedly retrieve it like a dog playing fetch. how was this exercise suppose to benefit the recruit to become a better fighting man? another lesson i couldnt understand, one recruit got sick and went to sickbay. a few minutes later the drill instructor told us the recruit died. he said sarcastically, one gone and 48 left! alot of the recruits were very sorrowful and emotional. an hour later the drill instructor told us he was just pulling our leg and the recruit will be fine. why he done this? was it a sick joke or was he trying to teach us something?