Niten Ichi-ryū
According to most traditional "kenjutsu" schools, only one sword of the "daisho" would have been used in combat. However, in the first half of the 17th century, the famous swordsman Miyamoto Musashi promoted the use of a one-handed grip, which allowed both swords to be used simultaneously. This technique, called "nitōken", is a main element of the "Niten Ichi-ryū" style of swordsmanship that Musashi founded.