Answer:
The earliest inhabitants of gochoseon (old joseon), which included today's peninsula of Korea, and portions of northwest China, migrated south about 5,000 years ago. There were subsequent waves of inhabitants that eventually established the first Kingdom of Goguryo in 57 BC. It is likely that the early villagers as well as the soldiers of the established army were trained in some forms of Martial Art combat. Early cave drawings, and writings indicate that during the three Kingdoms period (1st century BC to 7th century AD) contests were held at festivals involving hand strikes and grappling known as subak. Another early practice of kicking known as Tae kkyeon (aka "Tae kyon - the "kicking method") was unique to early Korean history. This was the impetus that later spurred the use of kicking as a primary weapon in modern Korean Martial Art, and the name change to Taekwondo which resembled the old name of Tae kkyeon.
In the 6th century AD, the youth of nobility were given the name Hwarang ("flowering men"), and given special training in academics, philosophy, literary arts, and skills common among soldiers such as horsemanship, swordsmanship, archery, and unarmed combat. Some Hwarang became educated political leaders. Others became military leaders and generals. It is through their loyalty to King, duty to country, honor to parents, and a code of bravery and ethical use of force that they became famous, and their philosophical ways were adopted by modern Korean Martial Art. Although there is no direct link to technical content of their curriculum, the tenets of Taekwondo, and the core principles of warrior philosophy, way of life, and code of conduct are based on the Hwarang of ancient Korea.