BTW, FDR had all the congressmen and senators who enlisted discharged and returned to Congress shortly thereafter.
All of them? I thought Henry Cabot Lodge, Jr. served throughout the war. However, now that I think about it, I have a vague recollection that he resigned his Senate seat and had to run to get back into the Senate in '46.
All the other members of Congress who wanted to serve were free to do the same thing and resign their seats. I guess they decided not to.
Strom Thurmond was of course at D-Day, but I don't think he had been elected yet to Congress at that point.