Most hostile interactions in our lifetime will fall short of physical conflict but that doesn’t mean aggression was never present. We hold a buffer around our bodies at a premium and yet others still fail to acknowledge this, and choose to move closer then we wish. Disrespecting someone’s personal space is a form of aggression and dominant individuals routinely ignore personal space buffers, in fact, it’s one of the ways they maintain their dominance! Invasion of personal space can even come from brief touching or pats on the back, but also from more inappropriate touching such as jabs to the ribs with fingers, pens, or worse yet, slaps to the buttocks! Sometimes space invades will gain unwanted closeness by using friendly conversation, that we naturally read correctly as feigned.
Overstepping territorial boundaries is obvious to almost everyone because most have at least a rudimentary ability to read body language. We can test proximity comfort levels by stepping only so close as that which causes the next party to step or lean back. Leaning back carries the same weight, as a message, as a full or partial step back, it is just more polite. We can use the step back technique to send this message to space invaders, but it is often ineffective, as their intentions are usually intended to yield such results. Stepping back, and then quickly placing an open palm on their wrist or arm, or hovering a hand palm-vertical near the midline between you and them will serve to anchor them, preventing further advances. Often, the only solution is to be outright with the invasion and call them out. In this case, we should expect it to cause openly negative feelings which could strain a relationship, so should be carefully considered.