Final answer:
The Knights Templar are typically considered the most successful holy order of the Crusades due to their key role in the First Crusade and the establishment and maintenance of Christian territories in the Holy Land.
Step-by-step explanation:
The Knights Templar are often regarded as the most successful holy order of the Crusades, thanks to their significant role in the First Crusade and their lasting impact. Founded around 1119, the Knights Templar were a wealthy and powerful order whose members were both monks and soldiers. Their purpose was to protect Christian pilgrims traveling to the Holy Land and to fight in the Crusades.
Their success in the First Crusade, when they helped to recapture Jerusalem and to establish Christian control over the region, marks a period of prominence for these knights. Despite later accusations of heresy and the disbanding of the order in the early fourteenth century due to political pressures, the Knights Templar's influence and achievements during the earlier Crusades stood out. They established a financial network that stretched across Christendom and set up many fortifications across the Holy Land to secure Christian territories.