Oda Nobunaga is one of the three men who are collectively seen as the men who unified Japan after the Sengoku period.
Oda (this is his last name) was not particularly high born. However, he had great ability and was able to become a military leader at a very young age. He then spent the rest of his relatively short life as a military man. By the time he was 26, he was the daimyo of his province. He then used military power and diplomatic acumen to gain control over much more of Japan. He was not able to complete the unification of the country, but he put it on its way to be unified by Toyotomi Hideyoshi and Tokugawa Ieyasu.