Shinkage-ryū

Shinkage-ryū (新陰流^?) meaning "new shadow school", is a traditional school (koryū) of Japanese martial arts, founded by Kamiizumi Ise-no-Kami Nobutsuna (上泉 伊勢守 信綱, 1508–1578) in the mid-sixteenth century. Shinkage-ryū is primarily a school of swordsmanship (kenjutsu and iaijutsu), and is a synthesis of Nobutsuna's studies in the school of Kage-ryū (Aizu). Shinkage-ryu can also refer to Kashima derived schools such as Kashima Shinden Jikishinkage Ryu and Kashima Shin Ryu.

Until the 16th century in Japan, martial techniques were concerned with effectiveness in real battle. At the time of the founder of Shinkage-ryū, Kamiizumi Nobutsuna, the superiority of a school was determined through duels. Basic postures were very distinct; very low, in protection of the body. The idea of winning at any price was deeply ingrained in the teachings of the schools that existed at this time. Primary philosophical and strategic concepts included the "sword that kills only once" (一殺の太刀, issatsu no tachi^?) and the "sword of only one cut" (一の太刀, ichi no tachi^?).

...
Wikipedia