After Silla unified the Korean peninsula in the 7th century, a new clothing style was introduced, which combined original Korean dress with foreign elements imported from China. This Chinese style of the Tang Dynasty (618 A.D.-907 A.D.) was regarded as an international clothing style, and was used for the uniforms of government servants and for ceremonial dress. The most conspicuous difference is that while the original Korean cloth had a straight neckline, the imported Chinese style had a rounded one. In the ensuing Goryeo (918-1392) and Joseon (1392-1910) periods, hanbok underwent various changes in terms of fashion, and the form that has been known since the time of Joseon. Koreans carefully consider their national identity in the Sirhak or “Practical Learning” movement of the 17th and 18th centuries, and in fashion, as in other fields, whatever was imported or influenced by foreign factors was subsequently Koreanized.