14. The Honjō Masamune was revered for more than five hundred years until it vanished at the end of World War II
Widely acknowledged as the greatest swordsmith in Japanese history, Masamune is believed to have been active in Sagami Province during the latter years of the Kamakura period of the late-12th and early-13th centuries. Producing several famous blades throughout his lifetime, the Honjō Masamune is considered by many to have been his finest creation and among the greatest swords ever made. Obtaining its name likely due to a connection to Honjō Shigenaga, according to legend Shigenaga was attacked in battle by Umanosuke. Splitting his helmet with the legendary blade, Shigenaga nonetheless survived and claimed the sword as his prize.
Later forced to sell the sword to Toyotomi Hidetsugu for thirteen large gold coins, despite being valued at more than one thousand, after exchanging hands several times by the Edo period the blade had passed to the Tokugawa family. Remaining in their possession until the end of World War Two, with Tokugawa Iemasa the last known owner of the sword, following Japanese defeat and occupation the United States ordered the surrender of all edged weapons. Presenting the Honjō Masamune in December 1945 to the authorities, the blade subsequently disappeared without explanation, with theories ranging from theft to inadvertent destruction by uninformed Americans ignorant of its value and historical significance.