We're having a doctrinal shift on this. Up 'til now we thought it was a best practice to retreat in the face of invaders. See this post:
The better answer is to stand and fight. Why?
First, putting rounds at the bad guys. I've practiced doing accurate double taps at the range. It's do-able, but too slow. I can put 16 rounds on target in about 30 seconds doing carefully aimed 2 round double-taps at 21 feet. I could do better with practice, but If I just empty the 16 round magazine at a dinner plate sized target (the size of a human chest) as fast as I can at the same range, I can get 10-12 rounds on target in in about 10 seconds, often faster. That shooting style is a lot more lethal for a non-expert shooter like me than carefully aimed double-taps, and that's the tactic we will use for handguns. Of course that's the secondary line of defense.
Second, retreat is a bad idea. There's no knowing who or what is outside. Better to fight it out on our turf rather than to divide forces, degrade communications, and give up the defense for an outside melee, or having to improvise the offense. At least on the defense we have planned fields of fire and kill zones, and know our way around.
So, to sum up: We're going to put a lot of rounds downstream as fast as possible, be good at fast mag drops and reloads, and use our familiarity with the ground to win fast.
Fuck you home invaders.