In case you're unfamiliar: "Jody" is a common American military slang term for a man who stays behind at home while a soldier, sailor, marine, or airman is off fighting. Jody gets to enjoy all the pleasures of home, including, usually, the girlfriends and wives of those overseas.
I'd imagine this phenomenon is not new, but I'd like to learn just how much it was openly discussed in the militaries of the past, what jokes and memes they had, and, on a more serious note, how fighters with significant others back home dealt with the worry of betrayal back in the day.
I can't speak to its universality as a concern, but I can point to some very old examples of the trope in Greek and Hebrew literature.
Both the Iliad and the Odyssey have themes of similar to this, although not quite what you're talking about. In Book 3 of the Iliad, Hector accuses Paris of starting the entire Trojan War and then not lifting a finger to actually fight it as part of shaming him into participating in a duel with Menelaus that will settle the war (Paris fights, loses, and then is spirited away by Aphrodite into the arms of Helen to recuperate; he also refuses to abide by the terms of the duel that he lost).
In the Odyssey, the eventual suitors of Penelope remain behind while Odysseus goes off to fight in the Trojan War. They move themselves into Odysseus' palace and begin exploiting its hospitality (including the implicit sexual assault of female servants). After Odysseus' colleagues return home, they begin trying to convince Penelope that Odysseus is dead and she should remarry one of them, who will then become king of Ithaca.
Along with these Greek examples, there's also the story of David and Bathsheba in the book of Samuel in the Tanakh. David, the monarch of Israel, is at home while the Israelite army is in the field, spies Bathsheba, and through a complicated plot arranges for her husband, who is serving with the army in the field, to be put at such risk that he is eventually killed. David has sex with Bathsheba who then gives birth to Solomon. Though the book of Samuel is 6th century BC, the sections with the David and Bathsheba narrative seems to be based on an older source much closer in time to the events it describes (but that source has not survived).