During Battle of Nagashino, Oda Nobunaga ordered his riflemen to make three lines and shoot in a certain order, that is the first line will shoot, followed by the second line. While the second line shoots, the first line will begin refilling their gun. By the time the third line finished shooting, the first line would be ready to shoot again.
This kind of formation enables his riflemen to shoot continuously. At that time, the way to fight riflemen was to let them shoot and then cut them down when they are refilling their gun. By having his riflemen shooting continuously, he successfully annihilated the Takeda cavalry.
Was Nobunaga the inventor of this formation? Or did he only made it famous after using it to great success? If so, then who was the inventor?