I suppose you could stretch Eisenhower since he was in the army in World War I (stateside), a general in World War II, POTUS (head of the military, technically) for both Korea and the beginnings of Vietnam, although that really escalated after he left office.
Hyman Rickover graduated from high school in 1918 and from the Naval Academy in Annapolis in 1922 so technically he was in the military for the First World War. He lasted until 1981 when the Reagan administration forced him out. So he would match the first.
David Hackworth served in WWII, Korea, and Vietnam - but I guess that’s probably not all that unusual a combination. I wonder if anyone served in all three of those and the 1st Gulf War?
Well, of course, there was Amazing Grace, Rear Admiral Grace Hopper, who served 43 years in the Navy, from 1943 thru 1986. She was retired (against her wishes) on the deck of the USS Constitution (‘Old Ironsides’), as the oldest commissioned officer in the Navy, on the oldest commissioned ship in the Navy.
When she wasn’t doing Navy work, she de-bugged Harvards’ Mark I computer (literally!), programmed UNIVAC I, created the first compiler for it, developed the idea of machine-independent languages, served as technical consultant to the Short Range Committee that developed COBOL (giving her the nickname ‘Mother of COBOL’), developed the first suite of compiler validation programs, gave many, many talks, and handed out a whole lot of ‘nanoseconds’. Amazing lady indeed!
Chesty Puller, USMC enlisted during WWI, and saw combat in Haiti, Nicaragua, WWII and Korea. When he was 17, only his parents’ refusal to sign a consent form kept him from combat in Mexico.
I couldn’t find it with a quick search, but I know we’ve done a thread on this in the past 2-3 months. While not American, I know Winston Churchill was mentioned in that thread.
My uncle as well. WW2, Korea, Vietnam. He was injured in combat in Vietnam when he was in his late 40’s and could have (should have) either been retired or at least serving in a desk job.