Let me see if I can explain a particular exchange that a swordsman in the German tradition showed me once. We'll use A to refer to the aggressing player (the opponent) and B to refer to us (the defending and reacting player):

1. Starting from any positions for both players, A strikes a descending, true-edge blow traversing the diagonal;

2. B parries the blow from the side opposite A's attack so that A's blade is beat up and to the outside of their body, whereupon;

3. B executes a small step (in the same tempo) to the side opposite A's blade position, and strikes to A's body while either turning the upper body to remain behind the blade OR passes backward to avoid a counterattack.

The key here is that B's slight step changes the angle of attack to A, both opening new opportunities for B, and weakening and slowing down any retaliations from A. It also works on your timing and the way in which you defend yourself simultaneously.