Japan, at last, was one — unified, united; no longer a splintered welter of "warring states" but an embryonic nation. The year, if it is to be pinned down to one, is 1590; the unifier, if one alone is to be named, is Toyotomi Hideyoshi (1536-98).
The beginning of the end of the frenzied, bloody, to modern eyes scarcely sane dance with death known as the Sengoku (Warring States) period (c. 1467-1603) was Hideyoshi's seizure of Odawara Castle in Sagami Province, today's Kanagawa Prefecture. Resistance crumbled. Hideyoshi was irresistible. He had subdued the "home provinces" around Kyoto, the capital; he had subdued Kyushu; the northeast, too, was his. He was as generous in victory as ruthless in combat. He slaughtered when he had to, but negotiated when he could, investing former enemies with land and authority, securing thereby their submission and loyalty.
What next? Peaceful enjoyment of the fruits of peace? Generations would pass before that came naturally. Japan was his. Peasant-born, he broke the mold. He was a great man. In Hideyoshi's day, greatness had one goal and one validation: conquest. Japan was conquered. What next? Korea, China. Why should they too not be his?