was a samurai commander in Azuchi-Momoyama period

Azuchi-Momoyama period

The came at the end of the Warring States Period in Japan, when the political unification that preceded the establishment of the Tokugawa shogunate took place. It spans the years from approximately 1573 to 1603, during which time Oda Nobunaga and his successor, Toyotomi Hideyoshi, imposed order...

 and Edo period

Edo period

The , or , is a division of Japanese history which was ruled by the shoguns of the Tokugawa family, running from 1603 to 1868. The political entity of this period was the Tokugawa shogunate....

.
His father was Kutsuki Harutsuna

Kutsuki Harutsuna

was a Japanese samurai of the Sengoku period, who ruled Kutsukidani Castle in Omi Province. He was a supporter of the shogun Ashikaga Yoshiharu. Harutsuna's descendants became daimyo in the Edo period.-References:...

 (朽木 晴綱). The Kutsuki were a powerful clan at Kutsuki-tani (朽木谷), Takasima-gori, Ōmi Province

Omi Province

is an old province of Japan, which today comprises Shiga Prefecture. It was one of the provinces that made up the Tōsandō circuit. It is nicknamed as .Lake Biwa, Japan's largest lake, is located at the center of the province...

.

At the age of two, Mototsuna succeeded when his father died in battle. At first, he served an Ashikaga shogunate

Ashikaga shogunate

The , also known as the , was a Japanese feudal military regime, ruled by the shoguns of the Ashikaga clan.This period is also known as the Muromachi period and gets its name from Muromachi Street of Kyoto where the third shogun Ashikaga Yoshimitsu established his residence...

 at the Hokosyu. In 1570, Mototsuna helped Oda Nobunaga

Oda Nobunaga

was the initiator of the unification of Japan under the shogunate in the late 16th century, which ruled Japan until the Meiji Restoration in 1868. He was also a major daimyo during the Sengoku period of Japanese history. His opus was continued, completed and finalized by his successors Toyotomi...

 when he attacked Asakura clan

Asakura clan

The ' are descendants of Prince Kusakabe , son of Emperor Temmu .The family was a line of daimyō which, along with the Azai clan, opposed Oda Nobunaga in the late 16th century...

 and retired through Kutsuki. He then served Hashiba 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...

 after Nobunga died in 1582.

In 1600 at the Battle of Sekigahara

Battle of Sekigahara

The , popularly known as the , was a decisive battle on October 21, 1600 which cleared the path to the Shogunate for Tokugawa Ieyasu...

, at the start Mototsuna took part in Ishida Mitsunari

Ishida Mitsunari

Ishida Mitsunari was a samurai who led the Western army in the Battle of Sekigahara following the Azuchi-Momoyama period of the 17th century. Also known by his court title, Jibunoshō...

's force belonging to Otani Yoshitsugu

Otani Yoshitsugu

was a Japanese samurai of the Sengoku period though Azuchi-Momoyama Period. He was also known by his court title, . He was born in 1559 to a father who was said to be a retainer of either Ōtomo Sōrin or of Rokkaku Yoshikata. He become one of Toyotomi Hideyoshi's followers...

. However, acting in concert with Kobayakawa Hideaki

Kobayakawa Hideaki

Kobayakawa Hideaki was fifth son of Kinoshita Iesada and the nephew of Toyotomi Hideyoshi.He was adopted by Hideyoshi and called himself Hashiba Hidetoshi and Shusen . He was then again adopted by Kobayakawa Takakage and renamed himself Hideaki...

, Mototsuna, along with Wakisaka Yasuharu

Wakisaka Yasuharu

' , sometimes referred to as Wakizaka Yasuharu, was a daimyo of Awaji Island who fought under a number of warlords over the course of Japan's Sengoku period....

, Ogawa Suketada

Ogawa Suketada

Ogawa Suketada was a daimyo in feudal Japan during the Azuchi-Momoyama and Edo periods.Initially Suketada served Akechi Mitsuhide and then Shibata Katsutoyo. After Katsutoyo died, Suketada served Toyotomi Hideyoshi. He was given 70,000 koku at Imabari, Iyo Province and became a daimyo...

 and Akaza Naoyasu

Akaza Naoyasu

was a Japanese daimyo of the Azuchi-Momoyama period, who served Toyotomi Hideyoshi. He was also known as and , and held the title of . His father, , was a retainer of Oda Nobunaga. Naonori was killed in action when Akechi Mitsuhide attacked and killed Nobunaga at Honnō-ji. Naoyasu then served...

, betrayed Mitsunari. After the battle, Ieyasu let Yasuharu govern his domain because of this exploit.