The 1587 battle of Sendaigawa was part of the Kyūshū Campaign

Kyushu Campaign

The Kyūshū Campaign of 1586-1587 was part of the campaigns of Toyotomi Hideyoshi who sought to dominate Japan at the end of the Sengoku period...

 undertaken by warlord Toyotomi Hideyoshi

Toyotomi Hideyoshi

was a daimyo warrior, general and politician of the Sengoku period. He unified the political factions of Japan. He succeeded his former liege lord, Oda Nobunaga, and brought an end to the Sengoku period. The period of his rule is often called the Momoyama period, named after Hideyoshi's castle...

 towards the end of Japan's Sengoku period

Sengoku period

The or Warring States period in Japanese history was a time of social upheaval, political intrigue, and nearly constant military conflict that lasted roughly from the middle of the 15th century to the beginning of the 17th century. The name "Sengoku" was adopted by Japanese historians in reference...

. The Sendai River (Sendaigawa) was among the final obstacles to Hideyoshi's attack on Kagoshima

Kagoshima, Kagoshima

is the capital city of Kagoshima Prefecture at the southwestern tip of the Kyūshū island of Japan, and the largest city in the prefecture by some margin...

, the center of the Shimazu clan

Shimazu clan

The were the daimyō of the Satsuma han, which spread over Satsuma, Ōsumi and Hyūga provinces in Japan.The Shimazu were identified as one of the tozama or outsider daimyō clans in contrast with the fudai or insider clans which were hereditary vassals or allies of the Tokugawa clan,The Shimazu were...

's domains.

Toyotomi Hideyoshi and his half-brother Hashiba Hidenaga met a Shimazu clan force, led by Niiro Tadamoto

Niiro Tadamoto

was a retainer of Satsuma daimyo Shimazu Yoshihisa. Jiroshirō is one of his other names....

, near the river. Despite being vastly outnumbered 5,000 to 17,000, Niiro led his men in a charge against the Toyotomi force, and even engaged the famous warrior Katō Kiyomasa

Kato Kiyomasa

was a Japanese daimyō of the Azuchi-Momoyama and Edo period.-Origins and early career:Kiyomasa was born in Owari Province to Katō Kiyotada. Kiyotada's wife, Ito, was a cousin of Toyotomi Hideyoshi's mother. Kiyotada died while his son was still young...

in personal combat before retreating under cover of night.