The Toyotomi crest, now the symbol of Osaka Prefecture.
The period of his rule is called the Momoyama period, after his castle. It lasted from 1582 to his death in 1598, or (according to some scholars) until Tokugawa Ieyasu seized power after the Battle of Sekigahara in 1600.
Toyotomi Hideyoshi was born at the place now called Nagoya. His given name was plainly "Hiyoshi". He was born with no traceable samurai lineage. As a youth, he joined the Oda clan as a lowly servant. He quickly was noticed for his resourcefulness and rose high enough to be given a full name: Kinoshita Tokichiro. Despite his peasant lineage, he quickly became one of Oda Nobunaga's most distinguished generals, eventually taking the name Toyotomi Hideyoshi. After Oda Nobunaga's death in 1582, Hideyoshi took control of all Oda territory within a year and was pronounced to succeeded him as military ruler and, aided by Tokugawa Ieyasu , had by 1590 ended the Sengoku period by reunifying Japan.
Hideyoshi wanted the title of shogun because it was then considered the title of the practical ruler of Japan. However, the emperor was unable to grant such a title to someone of Hideyoshi's lowly lineage. Then he wanted the Muromachi shogun, Ashikaga Yoshiaki to accept him as an adopted son, and was refused. Unable to become shogun, in 1585 Hideyoshi took the position of regent or kampaku just as the Fujiwara had. In 1591, he resigned as kampaku and took the title of taiko (retired regent). His adopted son Hidetsugu (actually his nephew) succeeded him as kampaku.
Before gripping control of Japan, he employed a friendly diplomatic stance with the Ming Dynasty and helped the Chinese government combatting the Japanese piracy along the coasts of Yellow Sea, South China Sea and Taiwan. Now with his country secured, he began the Battle of Bunroku to annex Korea. On April 1592, his generals invaded Korea. Within a month, the Japanese controlled almost the entire country. However, the Koreans soon rebelled, aided by the Chinese Ming dynasty. Resistance led by Yi Sun-shin forced the Japanese army to retreat from Korea on December, 1592.
Unsatisfied, in 1596 Hideyoshi unwisely attempted to invade Korea again in the Battle of Keicho. This time the Japanese encountered a well-prepared joint defence of Korea and China. The result was a stalemate.
In 1598 Hideyoshi died. The Japanese army withdrew and the battle ended.
This futile war caused the government to be led by another son, who succeeded him as regent, to collapse and be taken over by Tokugawa Ieyasu before power could pass to his underaged son and designated successor Hideyori.
But it is important to note Toyotomi Hideyoshi's overhaul of Japanese society. During the Sengoku period, it became common for peasants to become warriors, or even for samurai to farm due to the constant uncertainty of no centralized government. Upon taking control, Hideyoshi decreed that all peasants be disarmed completely. This solidified the social class system for the next 300 years. Furthermore, Hideyoshi ordered all of Japan to be surveyed, including a census. Once this was done and all citizens were registered, Hideyoshi required all Japanese to stay in their respective provinces (or 'han') without official permission to go elsewhere. These steps were taken to ensure a modicum of peace in a period of time where bandits still roamed the countryside and peace was still new. But also by surveying the countryside, Japanese land and resources could be utilized properly.
Politically, he set up a governmental system that balanced out all of the most power Japanese (or 'daimyo'). A council was created to include the most influential and powerful lords. While at the same time, a regent was designated to be in command; almost like a president with a parliament. At the time of his death, Hideyoshi had hoped to set up a system stable enough to survive until his adopted son became old enough to be the next leader. However, until maturity, his son was not old enough to rule. Tokugawa Ieyasu became the temporary regent. After much political maneuvering, Ieyasu managed to seize control of the country, ending Hideyoshi's legacy. But it is important to note: Togukawa Ieyasu left the majority of Hideyoshi's decrees in effect.