If attacked with a weapon it is likely to be either a blunt weapon, such as a stick baseball bat and the like, or a knife that can stab and cut.
The one who is armed has a huge advantage over an unarmed opponent/victim.
For that reason we do not talk about defence against weapons but only about the possibilities we have not to be severely hurt or killed.
We teach our members how to use blunt weapons and knives, primarily to teach a healthy respect/fear of these weapons, so that we do not make the basic mistakes if faced with an armed opponent.

It is often not a matter of winning but of what you may have to sacrifice in order to survive.
If possible, find a weapon you can wield or throw at the attacker, such as bottles, bicycles, chairs and the like. Also make use of obstacles in the environment to prevent the attacker from getting close.

Blunt weapons can be anything from a bottle to a baseball bat and the like. Blunt weapons destroys/kills with speed and impact and have the advantage of reach.
The most dangerous part of the weapon is the tip, therefore it is vital to get inside the arc the weapons tip travel.

Do not give the attacker a target, keep distance and do not stick the arms forward.
Do not attack but wait for the attacker to step forward to attack. At that moment, move into him without hesitation.

Be brutal! If someone attacks you with a weapon your life is in danger.

Do not exclusively focus on the weapon. Most people have 2 arms and can attack with both. Do not make it a fight for control of the weapon.

The Good News:

Blunt weapons requires a preparatory action making it easier for the defender to evaluate the angle of attack. Treat it as a swing (‘haymaker’), step across but think of the attackers hand as his elbow to prevent the weapon from continuing the movement. Remember that it is the tip that is most dangerous.
Stay close to the attacker and create maximum damage. If possible, secure the weapon and use the advantage a weapon can give (see later about blunt weapons against knife).

Cutting and stabbing weapons can be anything from kitchenware to boxcutters. They can kill/destroy with small flicks of the wrist.

NEVER GO INTO CLOSE COMBAT WITH A KNIFE-WIELDING ATTACKER.

NEVER TRY TO CONTROL THE WEAPON.

That said we may have to act if we cannot get away or if we have to protect others.
Keep distance to force the attacker to shorten the distance. Do not step into the attack. A knife-wielding attacker has a massive advantage in an in-fight.
Keep the arms back with the vulnerable parts towards the body to protect the throat, heart and internal organs. We can survive to be cut on the outside of the arms, not the inside where arteries and tendons are placed. Against a knife-wielding attacker it is not just a matter of winning but often a matter of what you may have to sacrifice.

Make short forceful attacks on the knife-arm and attack the throat, eyes or other high-value targets. Keep the distance unless the counterattack have been effective - in that case continue the attack and finish it.

Be brutal! If someone attacks you with a weapon your life is in danger.

Do not exclusively focus on the weapon. Most people have 2 arms and can attack with both. Do not make it a fight for control of the weapon.

The Good News:

Only this: Not everyone who pulls out a knife intents to use it. Move away, do not provoke.

‘Weapons training -
Every Saturday in the
Wing Tsun Center - Copenhagen’

‘Do NOT try to be a hero -
be somewhere else!’

When up against a knife-wielding attacker it is best to be armed, preferably with a blunt weapon (if you forgot your gun at home!)
Be aware of your surroundings - is there anything that can be used as a weapon or natural barriers that can be used to create distance and give you time.

The pointers are the same as in the 2 previous scenarios, with this extra point: Rest the weapon on the shoulder so it can be used without a preparatory movement as there is no time.
When the attacker moves in to attack, hit and move away at an angle, never in a straight line. Force the attacker to change direction.
Attack the side where he is holding the knife since it is difficult for him to protect himself and attack effectively at the same time.

In all situations:

If there are other people close by, make them aware of what is happening.
Is there anything in the environment that can be used as a weapon, either by wielding it or throwing it at the attacker, make use of it. Also make use of natural obstacles to create barriers and make it more difficult for the attacker to close in.

NEVER ATTACK - keep the distance and counterattack when the attacker moves in.

REMEMBER: There is no safe unarmed defence against an armed attacker. All we can do is to open a small window by avoiding the most basic mistakes, making it more likely that we can survive the assault. The more the attacker have trained in using weapons, the smaller our chances are.