So I need to dramatically increase my cardiovascular endurance

run every other day. do this til you can complete that distance is a good time
than do two days on, one off. continue til you can do it in a good time
increase days on til you can do it every day without hindering the next days run.
3 months is enough time to do this.
if you're doing this for military stuff, I strongly suggest doing weighted walks, pushups and pullups too. wouldn't be a bad idea to go to the gun range some too.

>>42853570
Yes on military. My endurance and some spiteful recruiters caused me to be temporarily discharged at one point, right before boot camp. I'm in it again for a second shot.

>>42853616
good luck anon. most noble career that im going to pursue when i graduate.