This study examined the East Asian international situation during the 2nd century, by focusing on the Yellow Sea pirate, Zhang Bolu, and explored the historical significance of his pirate activities. In March 111, Buyeo attacked Lelang Commandery of Later Han Dynasty while Goguryeo attacked Xuantu Commandery of Later Han Dynasty. Both countries mobilized their national forces and the kings themselves participated in the attack. It is highly likely that both countries mutually agreed on attacking Later Han Dynasty. Liaodong-Yemaek in Suzihe river basin joined Goguryeo, and Eupru which was subordinated to Buyeo also supported Buyeo too. In March 111, anti-Later Han forces rapidly expanded around the Northeast Asian countries. This study focused on Pirate Zhang Bolu for such international situations.
The Zhang Bolu forces grew through marine activities around Hebei and Shandong provinces. In 109 to 110, the forces grew their power around Shandong and surrounding regions. The Zhang Bolu forces also claimed them as an independent kingdom. In April 110, however, they left Shandong Peninsula and moved to southern Liaodong Peninsula because they were unable to withstand the attack of Later Han Dynasty. Nevertheless, the Zhang Bolu forces continued attacking southern Liaodong Peninsula and eastern Shandong Peninsula by centering on Miaodao Islands and Changshan Islands until the first half of 111. The maritime activities of Zhang Bolu forces blocked the direct transportation between Liaodong Commandery, Lelang Commandery, and Xuantu Commandery with the Later Han Dynasty from 109 to the first half of 111. The military forces of Liaodong Commandery were mobilized to fight against the Zhang Bolu forces while Lelang Commandery and Xuantu Commandery were isolated. In March 111, Buyeo and Goguryeo attacked Later Han Dynasty and it is considered that such attack was associated with the maritime activities of the Zhang Bolu forces. In April 111, Later Han suppressed the Zhang Bolu forces. The Later Han Dynasty organized Liaodong Commandery, Lelang Commandery, and Xuantu Commandery and Buyeo and Goguryeo established an amicable relationship with Later Han again. This shows that the international relations of Buyeo and Goguryeo, which were formerly anti- Later Han countries, were associated with rise and fall of the Zhang Bolu forces. The Shandong Peninsula, Liaodong Peninsula, and northwestern Korean Peninsula were connected with Myodo-Jangsan Coastal Routes in the early stage. Han Dynasty installed Liaodong Commandery, followed by Lelang Commandery to expand negotiation and trade.
As a result, Myodo-Jangsan Coastal Routes were built and operated as marine routes for general uses and surrounding regions developed with commerce and fishery. However, people were often overwhelmed because acts and taxes were forcedly imposed by centering on inland agricultural society. So, people living in the islands and sea left their lands. The several examples of pirates during 1st century to 3rd century show the independence of the sea world in contrary to the land forces. The Zhang Bolu forces during the 2nd century were associated with the East Asian international situation by reflecting the growth of Myodo-Jangsan Coastal Routes. This implies the historical significance of the Zhang Bolu forces in the sea world.