Ryukyu Exports to Ming China

From Maritime Ryukyu, 1050–1650, by Gregory Smits (University of Hawaii Press, 2018), Kindle pp. 115, 122-124:

By the late fourteenth century gunpowder weapons had become crucial in warfare. The Hóngwǔ emperor, “the gunpowder emperor” according to Tonio Andrade, embraced this powerful technology. “The extraordinary success of the Ming dynasty,” argues Andrade, “was based on the effective use of guns.” Sulfur was a key ingredient in gunpowder. Japan produced it in abundance, especially in and around Kyushu. China possessed abundant potassium nitrate (saltpeter) but lacked sulfur in a form that was readily usable. Therefore, sulfur had great profit potential as a trade item.

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The frequency of tribute trade increased dramatically after 1383. Total Ryukyuan tribute trade, including the number of embassies per year, number of ships, and quantity of goods, reached a peak during the 1420s and 1430s. Subsequently, it began a gradual decline, followed by a sharp decline during the 1520s.

No single metric captures the entire picture of official trade. The number of tribute missions per year is one possible measure, but each mission might consist of variable numbers and sizes of ships with different mixes of cargo. It is more useful to measure the quantity of sulfur, an item shipped with each tribute voyage. Ryukyu had access to a steady supply of sulfur from the island of Iōtorishima [Sulfur Bird Island]. Here, I follow Ikuta Shigeru’s analysis, with quantities derived from Rekidai hōan documents. Ikuta divides Ryukyuan tribute trade into seven periods, each based on significant changes in circumstances affecting the trade.

Period two was the approximate peak of Ryukyu’s tribute trade. The average annual shipment of sulfur to China on Ryukyuan tribute vessels during this time was 38,013 jīn. Using this quantity as 100 percent, table 1 shows the decline in Ryukyuan sulfur shipments to China relative to each immediate previous period and to period two, the peak of trade. Period three marks the start of Ming-imposed restrictions on Ryukyu’s tribute trade, the most important of which was limiting tribute missions to one per year. By 1440, once per year was already the typical frequency, so the practical impact on trade volume was small.

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Sulfur and horses help illuminate the maritime network in which Ryukyu was embedded and the role of wakō. Ryukyu’s tribute cargo of sulfur was not simply a token. Elemental sulfur was scarce in China, requiring that it be manufactured from pyrite, an iron sulfide. During the Ming dynasty “the number of areas producing pyrite-derived sulfur greatly increased. Ming dynasty documents (1564) mention that the emperor allowed the central and four local governments to buy about 10,000 jin of sulfur per year to replenish their supplies for gunpowder manufacture.”