East meets West in this innovative Japanese fire arrow known as the bo-hiya. The fire arrow is a basic projectile that found use across the globe for many centuries. Japanese warriors are recorded as loosing them from their bows (yumi) since at least the fifth century of the common era.
Gunpowder began to appear in Chinese armies in the 10th century and Japanese contact with the outside world—most tellingly, being invaded twice by the Mongols in the late 13th century—exposed them to new technology and the motivation to develop it for their own defense. Among the weapon concepts this exposure advanced was that of the fire arrow.
Japanese military technology got a fresh jump start in 1543, when the Portuguese established trade relations with Japan. Consequently the Japanese acquired European-style matchlock muskets or arquebuses, more advanced than the Chinese firearms they had previously used up until that point.
Besides reverse engineering muskets that gradually transformed their approach to warfare, the Japanese used Portuguese gunpowder technology to put a new spin on the flaming arrow—literally.
Arrows, with wooden shafts for carrying flame and deadly tips of metal to pierce foes, were given fins and repurposed to be launched from gunpowder weapons. Hemp rope, coated with an oxidizer such as potassium nitrate to render it waterproof but flammable, was wrapped around the shaft to form a fuze.
These powerful fiery arrows became known as bo-hiya. Some could be launched from cannons called hiya taihu while others, like this example, were fired from a type of tanegashima hand-held firearm called the hiya zutsu.
A multifaceted projectile, the bo-hiya was used on land by samurai gunners as well as at sea, where its ability to set wooden vessels aflame led to it becoming a standard shipboard weapon—used by both the pirates (kaizuku or wako) that preyed on maritime commerce and by the seagoing imperial samurai who hunted them down.