In a span of about 200 years, a group of knights became a powerful force in the Christian world and then were disbanded just as quickly as they formed. What is remarkable about them is their role in Christianity and how they lived their life day to day.
Interestingly, the knights who fought in the Crusades were welcomed back home and assigned to defend the regions of the Christian kingdom. Instead of living lavishly, the knights took vows of poverty. One would think that they would want rewards and land but they chose the contrary.
Noteworthy about the knights is that they were more like monks than like warriors. They took three perpetual vows, just one crusaders vow, and promised to follow the austere rules of the chapel and living quarters. The knights even wore similar dress to the religious clergy; they wore a white habit with a red cross on it.
Something that probably most people don't know is that the order in which the knights belonged to consisted of more than just knights. The knights were the highest ranked in the order, consisting of heavy cavalry, followed by the serjeants, who made up the light cavalry. The word serjeant is possibly the root of the modern word sergeant, which is similarly a rank in the military. But there were also non-fighting men in the order. There were the farmers and also the chaplains, whose job it was to perform spiritual tasks to whomever needed it.
The Templars were quick in growing because one who joined could engage in the two most popular issues of that time, "religious fervor and martial prowess." It's amazing how much they were respected in the religious community; they were granted exemptions on almost all their taxes, including tithes to the church. At the peak of their power the Templars defended many regions across Europe such as France and Palestine.
One can think of the Knights Templars as powerful in quality not quantity. The most knights to reside in Jerusalem were 400. But...