When I was in the military, way back when Soviets roamed the Eastern European plains, we ran an awful lot. Airborne outfits pride themselves on using their boots where more sensible service branches use trucks and buses, so we put plenty of miles on our issued running shoes every week. At my peak, I was able to do a 5K run in combat boots and with twenty pounds of gear in well under 30 minutes.
Well, that was then, and this is now. I have not been running on a regular basis since well before Quinn was born, and my attempts at getting back into it were all pretty short-lived because I tried to pick up right where I left off. There is no better way to sour on running than lacing up the old running shoes and setting out on a 2K run without gradually easing back into the exercise. You puff along for the 2K, you're completely winded and miserable halfway through, and then you kind of lose interest in getting up at 5am just to set your lungs on fire again.
I took some advice from a pretty good running website, which has a "Couch to 5K" running plan. You ease back into it by alternating running with walking at first...run for a minute, walk for a minute and a half, repeat for twenty minutes. Each subsequent week, the running stretches get longer, and the resting stretches shorter, until you can once again run 5K at a good pace without stopping.
I'd try the whole thing old school, in fatigues and boots and with a rifle, but I think KCSO may just take a dim view to a guy in military dress running along Emory Road at 5:30am with a rifle at port arms...