In 1575, Takeda Katsuyori, son of Takeda Shingen, attacked Nagashino Castle when Okudaira Sadamasa rejoined the Tokugawa and his original plot with Oga Yashiro to take Okazaki Castle, the capital of Mikawa, was discovered. Ieyasu appealed to Nobunaga for help and Nobunaga personally lead an army of about 30,000 men. The combined force of 38,000 men under Nobunaga and Tokugawa Ieyasu defeated and devastated the Takeda clan with the strategic use of arquebuses at the decisive battle in Nagashino. Nobunaga compensated for the arquebus' slow reloading time by organizing the arquebusiers in three rows, firing in rotation. Takeda Katsuyori also wrongly assumed that rain had ruined the gunpowder of Nobunaga's forces.