Oda Nobunaga (1534-1582) was a Japanese warrior chieftain who undertook the first stage in the military unification of Japan in the later 16th century after nearly a hundred years of disorder and disunion.

From the time of its founding in 1336 the shogunate (military government) of the Ashikaga family exercised at least theoretical military overlordship of medieval Japan. The first great leader of the Ashikaga, Takauji, established his headquarters in Kyoto near the imperial court and attempted to impose shogunate control over as wide an area as possible extending outward from the central provinces of Honshu.

But, as the result of a great struggle among the vassal barons of the shogunate from 1467 to 1477, this hegemony was completely destroyed. Although the shogunate was not abolished, it exercised little more central governance during the next century than the imperial court, which had been largely deprived of its ruling powers by the...