In 660, Silla and Tang forces captured Baekje, changing the balance of power on the peninsula. This alliance opened new channels for travel and exchange with Tang, helping set the stage for wider trade links by sea. It also drew Japan into regional politics because Yamato Japan supported Baekje’s restoration efforts.
In 668, the Silla–Tang coalition defeated Goguryeo, and Silla became the leading power over much of the Korean Peninsula. This political consolidation helped Silla expand state-controlled routes and ports for overseas travel. The period that followed is often called Unified Silla (668–935).
From 670 to 676, Silla fought Tang China to prevent direct Tang control on the peninsula. Silla’s victory helped preserve an independent Korean state, which mattered for long-term diplomacy and trade because embassies and merchants could operate under Silla authority. After the war, Silla’s overseas exchanges with Tang resumed and expanded.
Once Silla secured Danghangseong (also called Dangseong), it gained a key coastal stronghold linked to overseas contact with China. Control of this area supported maritime defense and made it easier to send envoys and goods across the Yellow Sea. The site later remained important as a long-term hub for maritime exchange and defense.
In the 7th–8th centuries, Silla’s major ports (including Ulsan and Danghangseong) connected Korea to Tang and beyond. These routes moved luxury and practical goods, as well as books and religious items, and helped Silla become part of wider Afro-Eurasian exchange through connected sea lanes. Maritime activity supported both commerce and the movement of monks and scholars.
By the mid-8th century, Japan’s Nara-period institutions preserved records and objects tied to international exchange. A set of Shōsōin purchase orders includes one dated as early as 752, and scholarship links these records to luxury imports connected with Silla–Japan exchange. This documentation is important evidence that overseas trade was not only diplomatic but also involved regular goods and procurement.
By the 9th century, thousands of Silla people lived in Tang China, especially in coastal areas such as Shandong and Jiangsu, where merchant activity was concentrated. These communities supported shipping, warehousing, and travel for traders and monks crossing the Yellow Sea. Their presence shows that Silla–Tang exchange relied on people living abroad as well as state embassies.
In 823, Tang authorities issued an edict to stop the slave trade in abducted Koreans and order their return to Silla, reflecting serious security problems tied to coastal banditry and piracy. This was a turning point because it shows maritime commerce also created risks for travelers and migrants. It also helps explain why Silla later invested in stronger sea-lane protection.
In 828, King Heungdeok authorized the Cheonghae garrison (Cheonghaejin) under Chang (Jang) Bogo. The base served as both a military headquarters and a trading hub, focusing on routes to Tang China and Japan while suppressing pirate activity. This institutionalized protection helped stabilize shipping in the Yellow Sea during the 9th century.
In 840, the Japanese monk Ennin traveled to Tang China and later recorded experiences that are used as evidence for conditions in the maritime world. Accounts about Chang Bogo and Silla-linked coastal communities show how travelers depended on organized shipping and protection to cross between Japan, Silla, and Tang. This illustrates that religious travel and trade used the same sea routes and support systems.
Chang (Jang) Bogo was assassinated in 841 at Cheonghae, ending a major source of organized maritime enforcement. His death mattered because his network had helped suppress piracy and stabilize trade between Silla, Tang, and Japan. Political conflict at the Silla court contributed to the loss of this powerful regional maritime leader.
In February 851, the Silla government closed Cheonghaejin and dispersed its troops, and records describe the relocation of remaining residents. The shutdown reduced centralized protection over key sea lanes, making trade more vulnerable to disorder. It marked a clear decline in Silla’s earlier, more coordinated maritime security posture.
After more than a century of relative stability, Unified Silla faced growing political conflict among aristocratic factions and social unrest in the 9th century. Such instability weakened the state’s ability to protect routes and manage ports consistently. As central control declined, maritime trade and coastal security became harder to sustain at earlier levels.
In 935, Silla formally ended when it handed over to the rising Goryeo state, closing the Unified Silla period (668–935). This transition matters for maritime history because the political framework that had supported Silla’s Tang and Japan sea links was replaced by new institutions and priorities. The end of Silla marks a clear endpoint for this phase of 7th–10th century maritime trade.
Silla Maritime Trade with Tang China and Japan (7th–10th centuries)