The Reactionary Gap: An Essential Part of Self-Defense

The reactionary gap is the space you keep between yourself and a possible threat, giving you enough time to respond if things suddenly escalate. It’s a simple concept: the more distance you have, the more time you gain. More time means more options. Less distance means less time and fewer chances to act effectively.

By maintaining that space, you give yourself time to recognize danger, decide how to respond, and take the safest action whether that’s creating distance, calling for help, or defending yourself.

Action vs. Reaction

When it comes to a confrontation, action nearly always outpaces reaction. Responding to a threat involves several steps seeing it, deciding what to do, and then moving. The more choices a person has to weigh, the longer the delay becomes.

This is explained by Hick’s Law (1952), which shows that reaction time increases as the number of potential responses grows. Fitts’ Law (1954) also applies, describing how accuracy usually decreases as speed increases when making rapid, aimed movements. These principles show why training is vital: practiced actions reduce hesitation and sharpen response times.

The 21-Foot Principle

In 1983, Salt Lake City Police Officer Dennis Tueller asked a critical question: how close is too close? Through testing, he found that an average person could cover 21 feet in about 1.5 seconds—the same amount of time it would take a trained shooter to draw and fire two accurate rounds.

This became known as the Tueller Drill or 21-Foot Rule. The point was never to set a fixed standard but to highlight how little time you have when someone with a knife or blunt weapon is within striking distance. Unfortunately, the idea was later misunderstood. Some assumed 21 feet always justified deadly force, while others thought force couldn’t be justified beyond that distance. Neither is true. Tueller himself clarified that the real lesson is situational awareness, not a hard rule.

In 2012, the TV show MythBusters tested the drill. They found that at 20 feet, a defender with a holstered firearm could sometimes get shots off just as the attacker arrived. At closer distances, the attacker nearly always struck first. And because their test subjects knew in advance what was coming, their results were still faster than what would happen in a surprise real-world encounter.

The reality: there is no single safe distance. Terrain, awareness, physical ability, skill level, and whether the threat’s hands are visible all affect the size of the reactionary gap you need.

Staying Ahead: Practical Safety Tips

Recognizing the reactionary gap allows you to take small steps that can make a big difference:

• Choose position wisely: Stand near exits or cover when possible to give yourself an escape option.

• Keep moving: Movement buys time and makes you harder to target.

• Use barriers: Physical barriers create

  both distance and protection.

These principles apply to both firearms and close-range weapons like knives or blunt objects. The closer you are, the fewer options you’ll have. The more distance you maintain, the more control you retain over the situation.

Final Thoughts

The reactionary gap is not a fixed number. It changes depending on the environment, the threat, and your own readiness. By understanding this principle and practicing awareness, you give yourself a critical edge in responding effectively when danger arises.