His Addison's disease and related health issues gave him an absolute out to military service if he wanted.

Instead of finding a doctor to write him a medical pass, he went doctor shopping for one to say he COULD serve, and then enlisted. He then insisted on a front line post, when his father's money and influence could have landed him a desk job during the duration.

His older brother also served, and died in a mission over occupied France.

And this photo was taken while Kennedy was suffering intense back pain after over-exerting himself in another public ceremony. Even so, he managed to pay his respects.