Check out StrongLifts 5x5 or Wendler 5/3/1, there are good apps for both. StrongLifts ramps up ridiculously and you'll probably plateau fast (I did), but I've been doing Wendler for a while and am liking it. You'll need access to a squat/press rack (or a Smith machine, but ughhh).
I recommend 5x5 for sure if you can get to a gym. You basically learn 5 workouts (squats, bench press, overhead press, barbell row and deadlift) and do those every other day. squats every day and alternate the other exercises. the app keeps track of everything and is free and extremely helpful. if you go this route eventually, it's important to warm up and the free version doesn't calculate what warmup weight you should use but it's pretty easy to figure out.
I had a lot of progress with this regiment (20lbs put on in like...4 months. and I'm someone who never gains weight and this was the good weight gain) but once I hit a certain point I was getting too sore to continue it at max. a buddy of mine recommended deloading the weight to 20-30% of the max weight rather than switching to 5/3/1. he swears by 5x5 though.
As for the tour life stuff, like Mig said, there are some quick body weight regiments that can really be good for that setting. There's a lot of super hero branded ones I found online that are good to just get you active and moving.
I just searched Nightwing Exercise on google and a bunch of these type of regiments came up...may require a bit of researching for some of the exercises but you can just check out a bunch of those types of exercises and see which you like
And like Mig said, push ups are huge. a friend of mine who is a regular gym guy told me doing pushups every day is a huge boost. "You will get strong, my friend." He mentioned how he had a tough time getting to the gym for awhile and just got some pushup bars and did that every day. I'm also a big advocate for squats as often as you can. Body weight squats are pretty easy to do and can be done anywhere. And the mentality I always have with stuff is, even if it's a slow day and you only do a few exercises, it's way more than if you didn't do any! Good luck, buddy!