This is drifting off topic, but I was wondering about the role of single combats. I have read a brief passage in a book on the Celts about single combats sometimes being used to settle an issue rather than a full scale battle.
I could be wrong, but I think this is ultimately quite relevant to the idea of whether warriors are born or taught.
With regard to the question of whether people shirked combat in the middle ages, you went to exaclty the right place by bringing up the celts.
From the iron age into classical times, European tribal societies such as the ancient Celts and later the Germans, as with many tribal societies around the world, were divided into three basic classes: warriors, farmers, and priests (druids & bards in the case of the Celts), with a smaller specialist fringe (such as blacksmiths) finding places along the fault lines, and slaves, mainly being captured members of other tribes. You can also see similar divisions in the Hindu caste system, and many similarities with some North American indian tribes.
There were these distinctions, and those who were willing to fight had a better standard of living and potentially could rise much higher within the society, but they were also much more likely to die in combat. All in all, though there were classes of a sort, all these folks were part of the same tribal society and lived together with a similar if not equal standard of living, usually with a democratic social organization.
Over time "civilizing" forces widened the gaps between the classes, to the point where you had slaves, and peasants ground down into being serfs on the one end, and elevated the warrior classes into the status of knights on the other. The idea of knights evolved from the Roman term equestrian, meaning roughly to be of middle class rank. It literally meant a citizen who could theoretically afford to fight mounted on horseback, though the Romans themselves had largely abandoned cavalry from early Republican days and relied on mercenary Cavalry.
So of course knights, being of the bellicose class, and forced into a martial lifestyle from an early age, would tend to be the more bloodthirsty, and willing to kill. Those who lacked this orientation could enter the clergy.
Members of the military class also watched each others performance in combat, and a willingness to take on risk, a true warrior spirit, was an important part of being a general, going back to the time of Alexander. Both Alexander and Julius Ceasar fought in the very front lines on occasions. I think the last vestige of this in modern times was when officers in the Civil war used to make a point of parading in front of enemy muskets to prove their bravery. If they survived their reputation led to a better chance of being promoted. Supposedly by World War II it was rare for an officer over the rank of Capitan to be anywhere near the front lines.
It's also interesting that by the middle ages and the Renaissance, the most successful peasant armies were of volunteers, especially tribal or clan based volunteer systems, as with the Swiss or the Scotts, say. Conscripted peasant armies were notoriously ineffective. It was also true in classical times, purportedly key to the succeses of the original Greek and Roman republican armies, and is still considered the case today, a 'volunteer' army such as the US and Britain have is considered superior to any conscript army, man for man (and woman for woman)
As for individual combat, this is a world wide tribal tradition, which was indeed practiced heavily by the Celts. It helped serve to cut down on casualties in the very frequent intertribal conflicts, which could otherwise have led to depopulation. Interestingly several Roman generals were challenged in this way and occasionally they accepted, and in some cases even won indidiual combat. Apparently they didn't win that often because it was officially banned by Roman law to accept such challenges somewhere around 100 BC.
JR