In 230, the island of Taiwan was reached by the Chinese during the Three Kingdoms period under the reign of Sun Quan. Contact with the native population and the dispatch of officials to an island named "Yizhou" () by the Wu navy might have been to Taiwan, but the location of Yizhou is open to dispute; some historians believe it was Taiwan, while others believe it was the Ryukyu Islands. Wu merchants also may have reached Southern Vietnam and Cambodia. Failed protection of Gongsun Yuan also was in existence when the latter rebelled against Wei. This was because of the waterway's difficulties. Such things cost Wu, and the achievements supposedly gained within Taiwan did not cover this problem and Sun Quan lost his vassal.