for its sharpness and resistance to breaking. Many swords made using these techniques were exported across the East China Sea, a few making their way as far as India. Issues of inheritance caused family strife as primogeniture became common, in contrast to the division of succession designated by law before the 14th century. Invasions of neighboring samurai territories became common to avoid infighting, and bickering among samurai was a constant problem for the Kamakura and Ashikaga shogunates. Sengoku period The Sengoku jidai ("warring states period") was marked by the loosening of samurai culture, with people born into other social strata sometimes making a name for themselves as warriors and thus becoming de facto samurai. Japanese war tactics and technologies improved rapidly in the 15th and 16th centuries. Use of large numbers of infantry called ashigaru ("light-foot", because of their light armor), formed of humble warriors or ordinary people with naga yari (a long lance) or naginata, was introduced and combined with cavalry in maneuvers. The number of people mobilized in warfare ranged from thousands to hundreds of thousands. The arquebus, a matchlock gun, was introduced by the Portuguese via a Chinese pirate ship in 1543, and the Japanese succeeded in assimilating it within a decade. Groups of mercenaries with mass-produced arquebuses began playing a critical role. By the end of the Sengoku period, several hundred thousand firearms existed in Japan, and massive armies numbering over 100,000 clashed in battles. Azuchi–Momoyama period Oda, Toyotomi and Tokugawa Oda Nobunaga was the well-known lord of the Nagoya area (once called Owari Province) and an exceptional example of a samurai of the Sengoku period. He came within a few years of, and laid down the path for his successors to follow, the reunification of Japan under a new bakufu (shogunate). Oda Nobunaga made innovations in the fields of organization and war tactics, made heavy use of arquebuses, developed commerce and industry, and treasured innovation. Consecutive victories enabled him to realize the termination of the Ashikaga Bakufu and the disarmament of the military powers of the Buddhist monks, which had inflamed futile struggles among the populace for centuries. Attacking from the "sanctuary" of Buddhist temples, they were constant headaches to any warlord and even the emperor who tried to control their actions. He died in 1582 when one of his generals, Akechi Mitsuhide, turned upon him with his army. Toyotomi Hideyoshi and Tokugawa Ieyasu, who