The Portuguese arrival in Japan in 1542 began a trade network that made foreign merchants and Jesuit interpreters indispensable to Japanese commerce. The exchange brought Cathay silk to a country with abundant silver, but it also gave Portuguese traders and priests leverage over Japanese access to that trade. The firearms they introduced likewise carried consequences beyond the marketplace, entering a society whose ideals of warfare initially rejected them.

Conditions for Trade

The Portuguese found a way into a trade that Japan and Cathay could not conduct directly. The two countries had long been in a state of war, and Cathay would not permit trade with Japan. Yet Japanese demand for silk was substantial: silk cloth helped make the hot, humid summers bearable, while only a small quantity of contraband had previously reached the country, at great cost.

The arrangement that followed joined Cathay silk to Japanese silver. The Emperor at Peking granted the Portuguese a small permanent base at Macao in southern Cathay and agreed to trade silk for silver, a resource Japan possessed in abundance. The Portuguese became the intermediaries between the two countries, and trade expanded until it touched the lives of samurai throughout Japan.

The Jesuits and the Price of Access

Commerce also depended on linguistic mediation. The Jesuits, most of them Portuguese, learned Chinese and Japanese and could negotiate and interpret between the trading partners. As the trade grew, their services became increasingly important. Japanese rulers therefore faced a practical constraint: tolerating the priests and the spread of their religion helped keep the Portuguese in Japan and the trade in motion.

That accommodation coexisted with suspicion and hostility. Yabu regarded the Portuguese as a tolerated necessity, not as welcome guests, and distinguished them from the unfamiliar foreign sailors who had fallen into his hands. He resented the foreigners’ control of trade and the resulting constraint on Japanese independence, even as the commerce served the interests of every samurai. The account describes powerful Christian daimyos and hundreds of thousands of converts, especially in Kyushu, near the Portuguese port of Nagasaki. Religious influence and commercial access had become interwoven, making the priests’ position difficult to separate from the trade itself.

Firearms and the Samurai Order

The Portuguese also introduced muskets and gunpowder. Japan began manufacturing firearms within eighteen months, although the locally made weapons were inferior to European ones. For a long time, guns remained novelties used mainly for hunting; even there, bows were considered more accurate. The slow adoption of firearms reflected a military culture built around ritualized individual combat and the honor of the sword.

Within that code, using a gun was regarded as cowardly and dishonorable. Samurai duty demanded honorable fighting, unquestioning loyalty to a liege lord, and fearlessness in the face of death. Yabu later saw the potential to turn the rejected weapon into a new military system: five hundred chosen samurai trained to fight as a musket unit, supported by twenty cannon and incorporated into an army of twelve thousand conventional troops. The proposal shows how an object introduced through foreign contact could unsettle the values that had first limited its use.

A Continuing Political Legacy

The trade’s wider setting was a contest over access to sea routes and the knowledge needed to navigate them. A rutter recorded courses between ports and coastal landmarks, soundings, currents, winds, reefs, anchorages, and the conditions for a safe return. Such directions were only as reliable as their pilots, copyists, printers, and translators, and could contain errors, even deliberate ones. Portugal and Spain guarded rutters for overseas waters as national secrets, while their Dutch and English rivals sought them. Commerce depended not only on goods and interpreters, but also on restricted navigational knowledge.

Later political negotiations reveal how trade, religious permission, and money could be used together. Toranaga promised the Jesuits permission to lay the foundation stone of what he called the Empire’s largest Christian temple on the forty-first day, while seeking their help in persuading Onoshi and Kiyama to support him. In another negotiation, Father Alvito proposed that the Portuguese Captain-General carry ten thousand ducats of Toranaga’s gold to Goa for investment, with half the profit going to the Captain-General. These later bargains do not undo the hostility surrounding foreign influence; they show the continuing political value of the commercial and religious connections established after the Portuguese arrival.