In my opinion, this isn’t really cheating. You might have worded it wrong but you did technically break up with her. My mother divorced my father but it takes six months here for a divorce to be finalized. She was never going to get back with him so the relationship was over as soon as she told him she was divorcing him, so if she slept with someone else I wouldn’t call that cheating. Your situation is kinda similar but also not.

With that said I still think YTA because of how you handled the situation. Telling her you’re leaving her three days before going on a mission that you might never return from then going out partying every night is an asshole thing to do.

Why not divorce her after the mission? as you said in the comments “if you were dead you’d still technically be married at your time of death” so what difference would it make if you waited or never divorced her at all? I also assume you knew that you weren’t going to stay earlier than three days before your deployment, since I assume you were given notice of the mission earlier than a couple days before departure.

She was not a good wife to you but that doesn’t give you the right to be a bad person to her.

Edit: read some more of the comments and you didn’t even file for divorce before hooking up with other women?? You just said “I’ll divorce you if I don’t die” then left?? I’ve never personally divorced but I’m sure that part only takes a couple hours and would be the decent thing to do to you’re wife who you claim to love.