Running after surgery

Question
I had to large moles removed from my back and chest. I do cardio work outs five days a week. Before I had the surgury I was running 8km no problem (pretty winded though) and now I'm stuggling with 5km. Usually on Mondays my platoon runs about 6km and then we do cross fit throughout the rest of the week. I'm 21, 6'2" and about 170lbs. Oh, my job function, I'm in the infantry (1PPCLI) so fitness is very important. My goal is to be back running 8km in good time as fast as possible. I think right now my fitness isn't that great, I can run all the runs but I can't keep up very well.
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The text above is a follow-up to ...

-----Question-----
Hi there,
I had some minor surgery at the begging of December and now I'm back running again. Being a good runner is actually very important to my job (I'm in the military) and now it seems I'm a horrible runner! Almost every time I go out now I feel like I'm going to throw up and about half the time I do! Now I think that maybe that might be because I'm pushing myself as hard as I can, but what would be the best way to get back into shape after over a month without running (and possible the fastest)?
-----Answer-----
Hi Mark
The first thing i need to know is past and present level of fitness and how much running you have done. I also need a bio,such as age height weight job function,what was the miner surgery,and what are your goals.Get me this info and we can pick it up from here mark.

All the best

John
former sgt.
USMC.A-1-6

Answer
Hi Mark
The most important run you could do now once a week is a long run at a easy confortable pace working up to one and a half hours to develope some endurance.The next run would be some speed work.I recomend working your way up 8 times 4 min. with a 2 min recovery at a pace that is hard but controlled and relatively confortable working your way into them once a week.This will give you some strength at a quicker pace than you normally run on mondays.Focus on these two workouts and i think you will see a quick transition.Any other questions get in touch mark.

All the best

John