You know all those legends of King Arthur’s knights searching for the Holy Grail and exemplifying Christian virtues? Before the Knights Templar, they wouldn’t have made much sense. In the earlier part of the Middle Ages, knights were seen as thugs, overrunning the countryside and looting villages to line their own pockets. The Knights Templar created a different model in which members were monks, sworn to poverty, chastity, and obedience, and committed to fighting “infidels” in the Holy Land. Promising to serve the Christian cause, they received papal recognition at the council of Troyes in Champagne in 1129. Significantly, in stories about the Knights of the Round Table written in the thirteenth century, the most perfect holy knight, Sir Galahad, wears a white shield with a red cross, which was the symbol of the Knights Templar.

Under “The Rule of the Templars,” a detailed code governing everyday behavior, the knights were required to live austere lives. They could have meat only three times a week, except on special holidays, since eating flesh was understood to corrupt the body. Fur and fancy clothes were forbidden. So were pointed shoes and shoe-laces, since “these abominable things belong to pagans.” Of course, chastity was a must, and Templars were forbidden to kiss any woman, even their own mother. Breaking the rules could mean getting a beating, being banished from the brotherhood, or having to eat meals on the floor.

During the Crusades, some Christian forces were ragtag armies with minimal training. Not the Knights Templar. They were highly trained, and became known as fierce fighters. They acted as the advance force in a number of battles of the Crusades, including the Battle of Montgisard, when they helped greatly outnumbered Christian forces defeat an army led by the great Muslim commander Saladin. A part of that fierceness probably came from religious devotion, which allowed them to see breaking their vows as a fate worse than death. The Rule of the Knights Templar called for them to never retreat, surrender, or charge without being ordered to do so—excellent features for any army that needs to remain disciplined.

While they were known for their piety and their readiness to fight for the spread of Christianity, the Knights Templar sometimes counseled their fellow Crusaders against rash action. European Christians reaching Jerusalem for the first time often wanted to do battle with Muslims as quickly as possible. The Templars, who had been in the area for years and had some friendly relationships with local Arabs, sometimes had to explain that picking a particular fight wasn’t a great idea. “It would not be unlikely that the Templars at times seemed insufferably know-it-all to those who had just arrived from the West,” according to Ann Gilmour-Bryson, a historian at the University of Melbourne. Of course, that didn’t make the Knights Templar any sort of pacifists. They just wanted to build up bigger armies so that they could effectively crush the Muslim forces.

While they were individually sworn to poverty, the Order as a whole became astonishingly wealthy. It helped that a Papal Bull issued by Pope Innocent II exempted them from paying any taxes. The Templars collected donations from all over Europe. Kings and queens gave them huge estates—Alfonso I of Aragon left them a third of his kingdom in his will. Regular people also made donations in their wills, leaving the Order small plots of land that added up. The knights ended up owning castles, farms, and a whole fleet of ships, as well as the entire island of Cyprus. They didn’t just hang onto these possessions. They used them to generate more wealth, trading crops, wool, and wine across Europe and renting land to tenants.

The initial purpose of the Knights Templar was to guard pilgrims traveling to Jerusalem, so they were well aware of the danger that robbers posed on the long journey. So they set up a system to help. Travelers could deposit cash at Temple Church in London and receive a letter of credit that they could redeem in Jerusalem. They also provided many other financial services for monarchs and elites. In the 1200s, they received the English Crown Jewels as security on a loan. And when King Henry III wanted to buy the island of Oleron, the Order not only brokered the deal but also collected installment payments from the king. The French Treasury also used the Templars as a sort of subcontractor for many of its functions.

Some scholars believe the Knights Templar helped import Muslim ideas that transformed Western legal and educational systems. For example, the Inns of Court in London, legal institutions formed in the medieval period with ties to the Templars, have some striking similarities to madrassas built around mosques, where Sunni scholars debated the law. This connection could help explain why English common law differs from Roman systems in significant ways. The system of maintaining colleges through a perpetual endowment may also owe its origins to Muslim models observed by the Knights Templar. The waqf, a legal device in Islamic law, similarly helped scholars maintain their independence in the medieval Middle East. Walter De Merton, a businessman with ties to the Order, founded Merton College, which pioneered this system in England.

Muslim forces retook Jerusalem in 1187, and over the century that followed the Crusader forces were driven from the Middle East. The Knights Templar established a new central base in Paris. But King Philip IV was not an eager host for them. The king was deeply in debt, and the Order refused to grant him new loans. The knights were also talking about forming their own state in southeastern France. By this time, the failure of the Crusades and the enviable wealth of the Templars had diminished their reputation. Where the Church has previously stood behind the Order, Pope Clement V now sided against them.

At dawn on Friday, October 13, 1307, French officials appeared at every Templar house in the country and arrested everyone there. The king had members of the Order tortured in true medieval style, using starvation, sleep deprivation, foot burning, and the rack. Under torture, the Templars confessed to all sorts of sinful and criminal behavior: spitting on the cross, kissing and sex between members of the Order, denial of Christ, and worshipping false idols. Over the next several years, dozens of Templars were burned at the stake. The Pope formally dissolved the order in 1312.

In the eighteenth century, fraternal organizations, particularly the Freemasons, adopted ideas and imagery from the Templars. Today, Freemasons can still become part of a fraternal order informally referred to as the Knights Templar. Members must pledge to protect and defend the Christian faith. The Order also shows up in all kinds of pop culture. In the video game Assassin’s Creed, the Knights Templar is presented as a shadowy millennia-old power. In Dan Brown’s The Da Vinci Code, they’re an equally shadowy organization still in operation in the modern era. The historic Knights Templar also inspired the drug cartel by the same name, which operated in Mexico in recent years. The gang published a rule book illustrated with crosses and knights on horseback which claims to bind members to a code of ethics, including helping the poor, respecting women and children, and not killing for money. The mystique of a politically and economically powerful organization with strong ethical guidelines based on religious piety is clearly an idea that speaks powerfully to many people more than 700 years after the end of the real Knights Templar.