As portrayed by Charlton Heston in El Cid
The Cid was a trickster, in the truest meaning of that word as applied to traditional myths. He deceives the Jewish pawnbrokers of Burgos, by hocking two huge chests full of sand and rocks, telling them that they contain treasure. He divests the Moslem citizens of Valencia of their property, their homes, their possession, their animals, but only in stages. At each stage he asks something more of them, but at each stage they say "well, at least that is all that he wants". Finally they had to leave the city with only the clothes on their backs. But it was all done honourably - for had they not agreed at each stage that what he was demanding was right and fair?
He recovers from his despicable sons-in-law, the Infantes of Carrion, his swords, his daughter's dowry, and finally their very lives and honour - but only in stages, being judged in court at each stage that what is being demanded is just and true.
And even in death, his last instructions are for one final trick - for his body to be strapped to his horse, for his death to be kept secret, so that the Islamist besiegers of Valencia will believe he is still alive and leading the charge, and that the Christian occupiers of Valencia may evacuate the city in safety.
But this code did not bind the Cid to honesty or fairness or equality or compassion. This is the aspect that contemporary Western readers find so very hard to understand. How can the Cid be considered so honourable, when he lies, tricks, tortures, plunders, and murders? It is actually the very same difference in values that bedevils relations between the modern west and parts of the Islamic world. For the traditional societies in Moslem countries work according to very similar rules that the Cid followed. Honour, to be defended to the death. Wife, to be chosen by the family according to its best advantage. One's female relatives, to be protected and defended only so long as they maintain the family's honour.
The Cid is vicious and cruel to his enemies. When the siege of Valencia begins to create famine in the city, the feudal lords of the town pressure the lower classes to leave so that the remaining food stocks may be stretched out. The Cid puts an end to that by capturing escapees, and burning them alive before the walls of Valencia. It is a clear message to the starving inhabitants that they cannot save themselves simply by leaving. And so the foodstocks are run down more quickly, to the Cid's advantage. When the city has fallen, he cruelly tortures the Alcayde of Valencia for days in order to find out where he has hidden his treasure.
The Cid was magnanimous and forgiving to those who give him allegiance. He shared the spoils of his raids with the citizens of the towns that give him shelter, be they Christian or Moslem. He respected Islamic law and allowed the Moslems to keep their mosques, their religious leaders, their legal systems. He gave generously to the Christian church. He gives precious gifts to those who have supported him.
To modern readers the Cid can be thought of as the Don Corleone of the eleventh century. He despoils the countryside of its wealth, its beasts of burden. But he only obtains through violence what he cannot obtain through politicking and trickery and bribery. He makes sure that the King and the Islamic governments are each given the mandatory fifth part of his spoils. But he obtains favour by giving to them a generous portion of the loot beyond the minimum.