That would be gunpowder and firearms. The gunpowder and especially firearms, changed the warfare in Japan during the Sengoku era which lasted <span>from 1467 to 1603 after which the period of the Tokugawa Shogunate began. </span>The first warlord to use then extensively was Oda Nobunaga who ordered 500 matchlocks for his armies. The firearms represented a huge tactical advantage.
