These two veterans made one of the most iconic moments in music history

When Johnny Cash took the stage at California's San Quentin State Prison on Feb. 24, 1969, one of the songs he would record there was destined to become one of Cash's most iconic songs, as well as one of his biggest hits: "A Boy Named Sue." It held the top spot on the country charts for five straight weeks and it was his biggest hit, climbing to the second slot on the Billboard 100 chart.

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"The Man in Black" was a veteran of the United States Air Force, a morse code operator who spent much of his career spying on the Soviet Union. In fact, Cash was the first person in the West to learn that Stalin died in 1953. As a matter of fact, his distinctive facial scar was the result of good ol' military medicine.

Related: Why Johnny Cash was the first Westerner to learn Stalin was dead

"A Boy Named Sue" is the story of a boy who was abandoned by his dad at a young age — after giving the boy a female name. Sue finds his dad at a bar years later and gets into a pretty nasty brawl with the old man. That's when his dad reveals he named the boy Sue so as to make Sue tough even when his dad wasn't around to raise him.

The song about a boy trying to kill his father probably resonated with Cash's audience that day.

The author of the song was also a veteran. Shel Silverstein, beloved around the world for his poetry, humor, and illustrations, was drafted by the U.S. Army to fight in Korea — but by the time he arrived the war was over. He was assigned to Stars and Stripes in the Pacific, part of the new peacetime Army. And thus a legendary military writer was born to the veteran community.

Now read: This famous author started his career drawing timeless cartoons as a drafted US troop

It was Silverstein who penned Cash's now-famous song about the boy with a girl's name, although Cash put his own twist on it. During the original San Quentin recording, Cash added the line, "I'm the son of a bitch that named you Sue!" In Silverstein's original writing, there were no curse words used. Even so, the "son of a bitch" line was censored out of the album.

Cash was doing what was known as a "guitar pull" back then — where writers take turns singing each other's songs. In fact, Silverstein recorded his own version of the song on his own 1969 album. Johnny Cash's band at San Quentin didn't even know it very well and did their best to improvise.

Silverstein notably worked with another fellow vet and country music superstar, Kris Kristofferson, on a few songs that were performed by country legends Chet Atkins and Loretta Lynn.