How easy is it to deflect a Medieval lance with another weapon? I heard it is possible.

I have seen XIXth century bayonet drills for infantry include a circular parry (sixte in modern fencing) to get your point into the cavalryman and his lance safely away. A lateral parry would also work.

Take a look here and here and here, any more questions?

Fiore has a bit on that. Click on "Spear against other weapons" and scroll to get to the part of infantry against cavalry spears.

http://wiktenauer.com/wiki/Fiore_de%27i_Liber...er_Weapons

also check out Thilo M's channel: https://youtu.be/V72zhvG6MeY

I am currently writing my master's thesis on this topic as we speak (well lance use in general). I will send ya some of the sources I am using.

http://wiktenauer.com/wiki/Hans_Talhoffer/W%C...a_134r.jpg
http://wiktenauer.com/wiki/Hans_Talhoffer/K%C...-3_52v.png
http://daten.digitale-sammlungen.de/0000/bsb0...;seite=355
http://daten.digitale-sammlungen.de/0000/bsb0...;seite=358
http://daten.digitale-sammlungen.de/0000/bsb0...;seite=360
http://daten.digitale-sammlungen.de/0000/bsb0...;seite=364
http://daten.digitale-sammlungen.de/0000/bsb0...;seite=368

So in summary, it seems to have been easy to do if you had the timing right. Since the couched lance was supported only at its rear end, it had no lateral support. In Fiore there is a counter to this, but it is unique to him and I haven't seen it anywhere else.

http://wiktenauer.com/wiki/Fiore_de%27i_Liber..._30b-d.png
So that you do not beat my lance out of the way,
Under my left arm I carry it in rest.

This is another counter of lance versus sword. In this one, the man with the lance couches his lance under his left arm, so that his lance cannot be beaten aside. And in this way he will be able to strike the man with the sword with his lance.

Since this lance is couched under the left arm and held with the right, it forms a triangle and it has lateral support. I have tried this with a friend and some broom sticks and you really can't knock it offline because the strong of the weapon is now what the enemy is trying to hit.

Problem is, the lance directly in front of you, that you are preparing to engage, is not the lance that's going puncture your spleen. So the discussion is fairly moot.