Anonymous Templar Knights

From Assassin's Creed Wiki

The anonymous Templar Knights are people found in all the locations of the game. Although they appear to be Knights they are all scattered which means that they are knights-errant. However if they are located near a European base they will rush to assist the other Europeans. A major but additional mission in the game wants you to kill them all. However they are much more trained and greatly armored so killing them will be a proven hard task. Near their camps the player can find horses.

One of the easiest ways to finish one off is to wait until he grabs you. Break the grab and if he falls over, switch to the hidden blade, and pounce him before he gets to his feet. Templars tend to grab often, so don't worry if you mess up first time, or he bumps into something and remains standing. Another easy method of executing a Templar Knight is to run in and 'tackle' one, knocking him to the ground. At this point, prime your hidden blade and remove the knight from existance.