GET OFF THE X
Meaning step to your left or right @ a 45 degree angle and deliver a powerful blow to the attacker twisting your upper body and leaning into the blow.
The Arm Bar is a successful defensive tactic which I taught frequently.
"Your options for a charging attack are to move off to the side causing your attacker to slow to turn to follow you, or to move forward at an angle, preferably on the non-weapon side, which will cause them to have to stop and turn. This will create time for you.
You need to train and practice those responses if you want them to be automatic under stress."
Lt. Dan Marcos offers his experience in martial arts for officers.
https://www.police1.com/police-training/articles/what-is-the-best-martial-art-for-you-jvs74lJP7nXokBwM/
Ground fighting is one part of defensive tactics providing officers the required skills if they are knocked to the ground. Learning to shoot from that position while fending off your attacker with your feet is another required tactic.
https://www.jonathanmccormick.com/about