“Wreak havoc. This is not the dojo. My targets of preference
for rear attacks, in order are knees, kidneys, neck and head.”
My comment on reading a situation before intervening is to click on your awareness to get a “read” on the situation. Some situations are obviously those to get involved in, some not. Then there is a situation set up in an armed self-defense class where the trainee comes upon a man holding a screaming struggling woman on the ground. Seems obvious. Surprise. When Galahad rides to the rescue and frees the girl, the reason she was being held down becomes apparent. She shoots him.
Dialing 911 on your cell phone might not be stupid. Hopefully it is the cavalry that comes so you don’t find yourself enduring calvary.
If you decide to wade in, how well equipped are you? I usually carry pepper in any somewhat risky environment and would probably lead with that. Any weapons of opportunity that the attackers haven’t already seized upon?
Remember you are barging in, probably from behind. It is unclear that any of the participants, including the victim, consider you welcome. Wreak havoc. This is not the dojo. My targets of preference for rear attacks, in order are knees, kidneys, neck and head. Practice your kicks recently? How about your strikes? You weren’t thinking of using your fists against anything hard, like a head, were you? And don’t try to reason with folks. Kiai might be more appreciated. If your initial attack is effective enough to leave a screaming “victim” writhing in pain, better. It is FAR preferable to have your initial onset sow panic in those who re-orient to your threat*.
A consideration for any aspiring Samaritan is that the observed attackers may have left a lookout/rear guard. Engaging an aware lookout is altogether different than attacking from the rear. The alarm raised, expect a more or less disciplined response from the main group.
If you are lucky and they just run away, you might consider doing the same thing in the opposite direction. Some jurisdictions might not view your intervention as humanitarian.
* The Siege of Vienna (1683) was lifted by attacking the Turkish rear. A surprise attack and disciplined advance routed the more massive Turkish army. Note – the Europeans had learned something in the wars of the Reformation which the Turks had missed. Anyone laying siege may be attacked from the rear, possibly besieged themselves.