This is an exercise designed by Cornelius Berthold, modelled on his sports fencing experience. Nothing new, and it may seem simple but is absolutely vital for self-preservation and control of timing and measure. I will explain step-by-step below:
1 Cornelius (left) is training to enter safely. He starts from Half-Shield. Myself (wearing a mask) is in Longpoint, and I will give the starting signal for this exercise. Note that neither swordsman can hit the other without taking a step. In terms of measure, each one could very well position his point right in front of the other one's face – but in order to hit, a step is required. We call this distance fencing measure. It allows to bind safely, as you cannot be hit (but neither can you hit your adversary without bridging distance by stepping, of course).
2 I lower my blade to move into Underarm. I am not stepping.
3 Cornelius spots that my blade is being withdrawn and the path is cleared, so he moves his front foot forward, by extending his leg. Note that the rest of his body remains static. He is not yet bridgeing distance and is not committing to a new position yet. Thus it would be easy to withdraw his foot if required. Plus, sneaking in with only the foot does not create a signal for the opponent as obvious as the whole body frame moving.
(Note that Cornelius is not yet in striking range, thus this is not moving in False Time.)
4 While reading the opponent, Cornelius begins to shift weight forward, bringing his extended weapons closer to the target. Note that he has not yet started to launch a blow. A strike which is initiated too early within a tempo (that is the relative time frame required for a fencing action) is easier to parry: the sooner the attack, the sooner the counter.
5 Cornelius delays striking as long as possible while bridging distance, all the while observing the situation. This way, he could instantly respond to any change of the situation. (For options, compare to I.33's First Play. Here is our interpretation as per November 2018.)
6 Only when he is absolutely sure that his opponent will be unable to counter his attack in time, Cornelius launches his blow. (In the above image it looks as if his blade is dropping back, but this is indeed part of a rather complex initial motion for his sturzhau)
7 As he strikes and hits, an adjustment step with his rear foot is being initiated.
8 With the completion of the action, Cornelius has adopted the same foot position as in the beginning, only now he is apparently in hitting range. He can now take a step back into fencing measure, and we can begin anew.
Also compare to this related article and video.