American Taekwondo Association, instructor designations are separate from rank. Black belts may be designated as an instructor trainee (red, white and blue collar), specialty trainer (red and black collar), certified trainer (black-red-black collar) and certified instructor (black collar). After a one-year waiting period, instructors who hold the sixth dan are eligible for the title of Master. Seventh dan black belts are eligible for the title Senior Master and eighth dan black belts are eligible for the title Chief Master. In WT/Kukki-Taekwondo, instructors holding 1st. to 3rd. dan are considered assistant instructors (kyosa-nim), are not yet allowed to issue ranks, and are generally thought of as still having much to learn. Instructors who hold a 4th. to 6th. dan are considered master instructors (sabum-nim), and are allowed to grade students to color belt ranks from 4th. dan, and to black belt/dan-ranks from 6th. dan. Those who hold a 7th–9th dan are considered Grandmasters. These ranks also hold an age requirement of 40+. In this style, a 10th dan rank is sometimes awarded posthumously for practitioners with a lifetime of demonstrable contributions to the practice of Taekwondo. Historical influences The oldest Korean martial arts were an amalgamation of unarmed combat styles developed by the three rival Korean Kingdoms of Goguryeo, Silla, and Baekje, where young men were trained in unarmed combat techniques to develop strength, speed, and survival skills. The most popular of these techniques were ssireum, subak, and Taekkyon. The Northern Goguryeo kingdom was a dominant force in Northern Korea and North Eastern China prior to the 1st century CE, and again from the 3rd century to the 6th century. Before the fall of the Goguryeo Dynasty in the 6th century, the Silla Kingdom asked for help in training its people for defence against pirate invasions. During this time a few select Silla warriors were given training in Taekkyon by the early masters from Goguryeo. These Silla warriors then became known as Hwarang or "blossoming knights". The Hwarang set up a military academy for the sons of royalty in Silla called Hwarang-do {花郎徒}, which means "flower-youth corps". The Hwarang studied Taekkyon, history, Confucian philosophy, ethics, Buddhist morality, social skills, and military tactics. The guiding principles of the Hwarang warriors were based on Won Gwang's five codes of human conduct and included loyalty, filial duty, trustworthiness, valour, and justice. In spite of Korea's rich history of ancient and martial arts, Korean martial