Did Knights if opposing factions avoid fighting each other on the battlefield assuming neither had a distinct advantage? Since Knights needed expensive heavy armor, expensive and well made weapons and we're generally well trained and an extremely valuable asset on the battlefield did they choose to avoid each other or would they not shy away from going face to face with each other or would they actively seek each other out for a battle?
Did it depend on the faction or "commanding officer"?
No, at least not in the periods I'm familiar with. In the high-late middle ages, knights generally sought out foes of equal social standing. To them, the peasantry were merely incidental, window dress for the REAL battle. That generally seems to have been the case in regular life as well, as we have accounts of knights tearing up the countryside in tournaments and general shenanigans from people like Thietmar and the Pastons, both of whom record incidents of that sort.
You see a similar thing in Japan, to draw a parallel. For a samurai, it was very dishonorable to be killed by a peasant or assassin, somebody with no 'name,' essentially. There was a somewhat similar concept in western European warfare/military culture at the time.
I had heard, although I cannot provide a direct source, from a college professor of mine that the English victories at Agincourt and Crecy, so famous now, were practically regarded as war crimes at the time by the nobility, since the English nobles were denied the chance to do honorable battle with the French. Both sides apparently occasionally rode down their own crossbow and bowmen too, particularly the French side since they were employing a number of Geonese mercenaries, who were regarded as double-scum for being both mercenaries AND commoners. If somebody else can confirm this, it'd be appreciated...or provide evidence to the contrary, in which case I'll happily withdraw the statement.
Whether one can argue distinctly that well trained and armed nobles would or would not avoid similar figures of martial sophistication on the battlefield, there was clear documentation of options for circumventing good armour to cause serious damage or restraint.
Master Fiore dei Liberi's treatise of 1409 describes a number of techniques designed to fight against an opponent in armour. In some places in the text, the caption states that the currently technique "may not work if he has good armour", and offers advice or points to another technique; in one instance, a thrust to the chest or face has failed due to a visor, so dei Liberi advises the student to attempt raising the opponent's visor and making the thrust again. Upper left illustration. Note that the other three illustrations are all non-lethal grappling techniques.
