We first have to define distance. Distance has been defined as physical distance between the two fencers measured by the extension and whether footwork (the lunge, and advance lunge) is needed to carry that extension of the weapon to target. Given the differences in overall reach, in sabre and epee the advanced target and multiple distances depending on the intended target, and the mobility of opponents, this has never been truly satisfactory. For example, a fencer can be at traditional medium (lunge) distance, but to catch an opponent have to deliver the attack by advance lunge inside the opponent’s response time and OODA loop.
The first change to thinking about modern distance is to reorder distance from further away to closer to the target. We do not start attacks at short distance with an extension. We have to get to the distance at which the extension can hit.
Second, there are two sets of distances, your and your opponent’s, and multiple subsets in epee and sabre, based on the target attacked and the target defended.
Third, we must include the opponent’s tactical intention in the equation. An attack met by the opponent collapsing the distance is no longer at lunge distance, and actually never was given the tactical intent of the two fencers.
Fourth, we need to use actual tempo as a determinant of the distance. An attack with an advance-lunge, even a fast accelerating advance lunge, is a two tempo action and inherently takes longer, and is thus tactically slower than an attack with a lunge. This is regardless of how the rules define an advance lunge for right of way purposes.
And finally, there are three special cases. Counteroffense occurs within a tempo. Infighting distance and passing distance are two special cases in which the action occurs regardless of tempo (infighting) and as an expanding tempo (passing).
So what is a better approach? The old division into 3 or 5 distances is less relevant in modern fencing than an approach based on the fluidity of action. I suggest distances that are actual envelopes of space and time:
Preparation distance – distance at which preparatory foot and blade work are required to get to the distance at which you can expect to hit the mobile opponent in a two tempo action (with tempo being defined actually as the time to complete a simple blade or footwork action regardless of how the rules define tempo for right of way purposes).
Two tempo distance – distance at which you can hit the opponent on the desired target with a two tempo attack. This may be the old out of distance if the opponent is stepping forward or the medium distance if the opponent can be expected to retreat under attack. For the defender, this is the distance at which either blade preparation or the final action can be defeated and in which the defender’s action can control the tempo required for the riposte.
One tempo distance – the distance where a one tempo blade action or combined one tempo blade and footwork action can result in a hit. This can be anywhere in the old advance-lunge or lunge distances. For the defender this is the envelope to defeat the final attack or the distance at which the advanced parry intercepts the early development of the attack.
Inside tempo or counteroffense distance – the distance at which the fencer under attack can hit with counteroffense. With fast footwork this can be anywhere in the attacker’s two or one tempo distances. The defender is operating literally within one of the attacker’s tempos.
Infighting distance – the distance at which tempo is largely irrelevant, the action is confused with multiple attempts to place the blade, and unusual attitudes are required to reach the target.
Passing distance – the opening distance as the opponent is past the defender and in which the referee’s assessment of the immediacy of the defender’s attempt to hit becomes the dominant factor as to whether there the hit is allowed.
This approach requires a good tactical understanding of both the attacker’s and the defender’s courses of action by both fencers, identifies the category of actions each will need, accounts for both fencers’ movement, and sequences the distances in the actual flow of the bout to start where the action starts. It is not something you teach in a beginner’s class. However, for intermediate and advanced fencers it should make distance more relevant, not just something you read about in the first chapter of a fencing manual.