I was scatting in my father's library, and I found an old book about the European history in the era of 11-13. century. It has an interesting section which explained many things...
"In the century of the eleventh, a monk arrived from the far East into Europe. No one knows who this monk was, according to the legends he was a fallen monk who lost his faith and left his monastery. He was a master of the deadliest marital art of his era, the infamous "White Lotus Kung-Fu". This monk taught his marital art to anyone who was able to pay the price. After a few years of wandering, he disappeared without a trace, no one knew where he went. In the beginning only the nobles were able to use it, but to the century of the thirteenth, this ancient marital art was used even by the peasants, bandits, etc. It spread across Europe, and even arrived o the Middle-East and to the cold mountains of the north.
The White Lotus Kung-Fu has the following characteristics (The monk taught the defensive techniques only. We do not have records about any offensive technique used in Europe.):
When the user poured KI, or as many know, spiritual energy into his shield, the shield were able to pull arrows into his center. With the help of this technique, the user was able to avoid a fatal shot to his body parts which weren't protected by a shield.
When the user did not have a shield, he poured KI into his weapon. With this, he received the ultimate melee defense. With this weapon, he was able to parry any melee attacks, including lances of a charging knight, but it didn't protected the user against missile weapons.
After the invention and spread of the firearms, the White Lotus Kung-Fu wasn't practiced anymore by the public, but according to a few records, secret societies still practicing it in these days too."
Well, I think this book explained many aspect of Warband. The shield force field and the insane parrying abilities.