Does smoking help you run better or breathe better?

I joined the army and i made it a point to avoid smoking because of all the health issues associated with smoking, but i slipped over the past month and smoke 3-5 cigarettes a day. yesterday i ran a last minute PT test without any training and i managed to get one of the fastest run times i ve got my whole career, 12:38. and my breathing was fine, it was the endurance of my legs that was suffering at the end.