Within a few years of the discovery of the sea route to India by Vasco da Gama in 1497/98, the Portuguese had built an extensive network of bases in the Indian Ocean stretching as far as the Strait of Malacca in the east. Although word of the wealth of China and Japan had fired the imaginations of Europeans since the reports of Marco Polo, forging commercial relations with these empires initially proved difficult.

When the first Portuguese arrived in Japan in 1543, the country was riven by conflicts between regional princes (daimyo). Some of them welcomed the Portuguese as tradin…