Last night in training we were doing the zombie drill which is a tactical game to prepare the Kravist for multiple attacker situations. Being aggressive and taking the initiative cannot ring more true than in a situation when faced by multiple opponents. If you do not attack first than you will certainly be overwhelmed as the attackers blind side you and attack all at once. It is important to have situational awareness of the range and position of the assailants.
If possible my advice would be evasion. It is very unlikely that even a skilled fighter will prevail in a situation where he faces multiple opponents. I have seen a few clips on YouTube where one man manages to fend off several attackers. I am a little suspicious of the authenticity of a lot of the material, it shows the guy taking the initiative and attacking aggressively mostly using boxing skills. In making the decision on whom to attack first you have to analyse who is at closest range and presents most danger. Obviously the one moving to your blind side would be the one you should be wary of.
Attackers are not fighters, they are predators. The time that someone got stabbed in the face in the nightclub when I was on duty, the attacker plunged the blade into his victims face whilst he was distracted speaking to someone else. If someone having the advantaged of an edged weapon uses this kind of deception you can be certain that a sucker puncher will do the same. If possible never get caught up in the middle of the assailants; that’s the whole principle of the drill that we practice. Always move in the direction where the others have to get through their accomplice to get to you.
In Krav Maga we often control the attacker whilst throwing knees, in this position it is possible to swing the attacker round controlling his body and using him as a shield thus preventing other attackers from attacking you directly. You can push or throw the attacker into his friends and make a break for it and escape. If in a bar you can knock over tables and stools and use them as barriers to hinder your attackers to make an escape. On the street you can probably use things like trashcans and garbage bags.
Look for weapons of opportunity like bottles, tumblers, plates and ashtrays to strike and throw at your assailants. The main emphasis is to focus on evasion.
Tactical issues to take into account would be to take out the first guy with extreme aggression. This has the benefit of making the rest feel discouraged at the risk of getting hurt and also they may choose to help their downed friend thus distracting them form attacking you. Injuring someone has a great psychological advantage particularly when a crowd of thugs sees what looked like cheap entertainment turning into a fight for survival. Spilling blood generally gets the message across pretty well. Take out anybody who stands between you and the escape route. Any weapon skills would be a great advantage. Stick and telescopic baton is one of the weapons that I train in which can be used in this type of scenario.