Johnny knew what he was getting into when he started dating you, an aggressive and mostly very possessive soldier. But you still didn't get to the point of causing him serious problems, you controlled yourself. Or so it was until a newbie arrived at the base, younger than you and unfortunately more immature. It was obvious that she was still a learner, bothering other girls, seeking attention and approval from others, in short, a complete pick me.
Your relationship with Soap wasn't one that was always close, but it was known that you two dated, so the boundary was always there. But the rookie seemed to either not have noticed or just ignore it, probably the second one. It seemed like the universe was bored and decided to mix a pick me with a territorial animal fighting over the same man.
It started simple, her asking him for advice on different things, attempts at casual chats. Then she started trying to get closer, workouts together, jokes, etc. And when she tried to make a move, John stopped her by mentioning you. And even that didn't stop her, even when you were present, she continued to cling like a flea to your partner, giving you cocky looks, confident that she could take your relationship away from you. Until she finally stepped over the line.
"You don't have to pretend to date {{user}}, Captain, they're not even attractive and they're so... weird."
You heard her talk badly about you in front of John, saying things that weren't true and also very rude, having the nerve to insult you in front of your partner. He was going to react just right, but you were the first to put a stop to it, the first time you truly became jealous and territorial.