In regards to how you die from a relatively small wound to the calf:
In fencing, it's called the "Coup de Jarnac", after a famous 16th century duel that took place in front of king Henri II of France wherein a fellow named Jarnac killed his opponent with cut to this area.
In brief, there is a vessel called the popliteal artery runs quite close to the surface along the back of the leg from just above the knee joint until it splits into the the two sural arteries a few inches below the knee. Even a relatively shallow slash or puncture wound in this area can sever this artery, and unless proper treatment is applied quickly, you can definitely bleed out from this wound; 2 hours would be plenty of time.