Wyocarp-
It's hard to imagine how fast something can go down unill it actually does. Take this event that happened to me just this past Saturday...
I'm a musician. We had just finished our set and were waiting for 2am to roll around so we could load up the van because the place was packed with people. At 2, the bouncers started kicking all the drunks out, which is totally normal. These two guys were giving one of the bouncers trouble, mainly just talking trash, but still more trouble than usual. After a few minutes of macho jackass talk, they back down and leave.
So we get the van packed up and I go back in the bar for a once over to make sure we didn't forget anything. Two of the five band members were out with the van while two of us went in to do the once over. I got about halfway to the stage when someone from out back called out to us that someone was messing with our van.
The singer and I run out and those same jackasses from earlier were trying to rip the windshield wipers off our van and our guitarist and drummer stopped them. One of the guys was nose to nose with our guitarist and the other guy just kept saying "stay out of it" and "just let them fight".
Let me set the stage from my point of view. We were working, albeit playing music and having a good time, but it's what we do for a living. I was completely sober (I don't drink at all) and so was the rest of the band. We had just come out of a bar, which meant that my pistol was locked in my car across the parking lot. I had a knife, fists, and my most important self-defense weapon - My Brain. I've been doing this sort of thing for years, and this wasn't the first barfight I'd been to and unfortunetly it won't be the last because it's kind of a occupational hazard. From experience, I didn't think this guy was going to do anything. He was drunk and there was 5 or 6 of us and really just one of them since it didn't seem like his friend was into it.
So then this guy totally goes for it and tries to tackle my guitarist. I'm standing right next to them, our backs were to the van (Mainly so no one could come from behind). I'm still in the "I'm going to break up the fight" mindset so I move to grab the guy and pull him off. From out of nowhere his friend hits me and rams me into the van, pinning me. So my left side (arm and all) is jammed up against the van so with my right hand I give the guy a hammer fist, break his nose, and he drops to the ground.
Now that the friend is out of the picture, we kick the crap out of the other guy trying to get him off the guitarist because he just won't let go. Eventually he lets go and they stagger off. They come back a few minutes later, but we're all inside because the cops are on their way.
So I learned a lot from this encounter. It had been over two years since something like this happened. Here's what I learned and how it applies to the OP:
-I was in code burning-hot-like-the-sun, and I still didn't see the guy's friend coming for me. You can't expect yourself to be looking everywhere at all times. It's just not reasonable.
-A guy smaller than me had my left side pinned against that van. Had he had a weapon and I would have not been carrying with a round chambered, that'd been it for me. It's all too easy for someone to do the same thing in any parking lot with the intent to carjack or mug or just kill for the sport of it.
-Last and most importantly, this whole this took place in less than 2 seconds. The friend came around to my side, hit me, pinned me, and got his nose broken in less time than it took for my guitarist and the guy he was tangleing with to hit the ground.
I learned a lot more from this encounter, really just re-enforced things I already knew and made clear why I do some things I do. But they're not relevant to the OP, so I left them out.