This is when the potential of a confrontation materializes. The moment right before a neutral situation becomes a combat or in this case, a defense situation. Where the dynamics of the scenario is altered and therefore you must assess what level to countermeasure. Pre-engagement is not a level.
This level is to not engage the assailant(s) at all, if the scenario makes it a viable option – by way of evasion. To escape the vicinity and into a safety. Complete avoidance of confrontation or not becoming a target at all. For the sole purpose of self-preservation, this is the best possible self-defense strategy.
This level is similar to non-engagement as evasion is the goal but differs as in this scenario, confrontation is unavoidable – meaning the assailant(s) has you trapped, cornered or in some sort of control. The countermeasure here is to deploy resistance specifically in a way to find a way to escape.
This level is to directly engage the assailant(s) to not to escape, but to overcome by incapacitation. By using countermeasures of equal or greater force to immobilize them to effectively put an end to the altercation and therefore their ability to cause you further harm. To eliminate the situational danger.