A document written by a Dutch trader on the "Siege of Osaka" (1614-1615) in which Tokugawa Ieyasu overthrew the Toyotomi clan, has been found in the Dutch National Archives in The Hague, the Netherlands.

The discovery was announced by the Kyoto-based International Research Center for Japanese Studies on Sept. 21. Part of the document describes a beleaguered Toyotomi Hideyori pushing daimyo (feudal lords), who were trying to defect to the enemy, off a castle wall. An expert says, "It is a precious document that gives us a glimpse of the situation surrounding the Siege of Osaka."

The document itself is a letter written by a person working for the Hirado Dutch Trading House established by the Dutch East India Company in 1609 in Hirado, on a small island that is now part of Nagasaki Prefecture. Some documents had already been translated into Japanese, but the International Research Center for Japanese Studies launched fresh research jointly with a Dutch university on other documents written between 1609 and 1633.

The letter on the "Siege of Osaka" was written by an employee of the Dutch East India Company to the head of the trading house about one week after the Toyotomi clan was destroyed in the summer of 1615. It was apparently based on information obtained through interviews with subordinate warriors of feudal lords and merchants in Osaka and elsewhere immediately after the fall of Osaka Castle.

The document says that several lords loyal to Toyotomi Hideyori, the son and designated successor of Toyotomi Hideyoshi, thought that they would be pardoned and set fire to Osaka Castle in order to defect to the side of the "emperor," or Tokugawa Ieyasu. But they died on the spot after being pushed off the castle wall by Hideyori. In the end, it was impossible to put out the fire they had started, so Hideyori and other daimyo, who had lost the courage to fight on, killed themselves by seppuku, allowing the emperor, Tokugawa Ieyasu, to regain the castle, the document says. The letter also says that about 10,000 people including Hideyori's soldiers lost their lives.

Makoto Atobe, chief curator at the Main Tower of Osaka Castle, said, "There are documents that describe the betrayal by Hideyori's vassals, but I have never seen any descriptions of Hideyori having pushed them down from the castle wall. The document is significant in that it is an objective description through the eyes of a foreigner."

Frederik Cryns, associate professor at the International Research Center for Japanese Studies, said that he wants to conduct more research to shed light on the situation in Japan at the time.