For James Stewart, his military career is not simply a side note. Though he was a wildly famous actor, he also managed to be a pilot within the United States Air Force in not just World War II, but the Vietnam War, too. If there's one thing Stewart was, it was dedicated. He was drafted into the United States Army in 1940 but failed to make the cut because he was underweight. Most men would have shrugged their shoulders and moved on, but not Stewart. He sought out trainers to help him gain weight.
Somehow, Stewart was maintaining his career as an actor while also serving his country. When the Vietnam War came around, Stewart didn't abandon his duties. He was a high-profile actor at the time and didn't participate to the level that he did in World War II, but he was still present.