Although Korea has a long history, voluntary contacts and exchange with other countries were largely limited to China for some 2,000 years. From China, Korea adopted its political, social, religious, and artistic traditions. When the Korean Peninsula was unified by the Shilla Kingdom in A.D. 676, Buddhism became the dominant religion, and remarkable achievements in architecture, sculpture, painting, and philosophy were made during this era. Confucianism was introduced in the sixth century, influencing the governmental and educational systems. When the Koryo dynasty was founded in 918, Buddhism became the national religion. With the founding of Yi dynasty in 1392, Confucianism was adopted as the major guideline, not only for official and political functioning but also for the private life of the people.