He was born into a family of local landholders in Hachisuka, Kaitō District, Owari Province (now Ama, Aichi). He is known by the common name Koroku. Some records say he was one of the "Kawanami-shū" engaged in transport on the Kiso River, but this is not certain. His mother is said to have died when he was small.
After his father died, Masakatsu left his home and served close to Saitō Dōsan of Mino. He was often employed by Dōsan in the conflicts between Owari and Mino, and his first name, Toshimasa, seems to have included a character received from Dōsan. At this time he stood on the opposite side from the Oda of Owari.
In the Battle of Nagara River, fought between Dōsan and his son Saitō Yoshitatsu, Masakatsu fought on Dōsan's side. But Dōsan was defeated and died. Masakatsu then served Oda Nobukata, lord of Iwakura Castle in Owari, and is said to have been given a robe as a reward for helping put down a revolt in the castle.
When Kinoshita Tōkichirō, the later Toyotomi Hideyoshi, built a castle at Sunomata for Oda Nobunaga's campaign against Mino, Masakatsu and his brother led their riverside comrades to help. Afterwards, as an auxiliary under Hideyoshi, he served as a guide in winning over Saitō warriors and was rewarded with lands by Nobunaga.
Through Hideyoshi's arrangement, Masakatsu's daughter was engaged to Shōjumaru, eldest son of Kuroda Yoshitaka (Kanbei), later known as Kuroda Nagamasa. By making relatives of these two chief vassals, his right and left arms, Hideyoshi sought to strengthen the unity of his retainers. This year Masakatsu also joined the campaign against the revolt of Araki Murashige.
During the Chūgoku campaign, Hideyoshi besieged Miki Castle in Harima for a long time to starve it out. Masakatsu defeated the Kobayakawa forces of the enemy Mōri at Ōmura as they tried to bring provisions into the castle, cutting off its food supply. This action played a major role in taking Miki Castle.
Together with his son Iemasa he captured Nagamizu Castle in Harima and for this became a castle lord for the first time. When Harima was pacified, Hideyoshi made Himeji Castle his base and gave Masakatsu Tatsuno Castle with 53,000 koku. Masakatsu, who had risen from a local landholder in Owari, had at last become the master of a castle.
In the siege of Bitchū Takamatsu Castle by flooding, Masakatsu handled negotiations with the Mōri side together with Kuroda Yoshitaka. When Nobunaga fell in the Honnō-ji Incident, he strictly kept the news from reaching the enemy on Hideyoshi's orders and concluded peace with the Mōri. He then marched back with Hideyoshi's great army and fought at the Battle of Yamazaki.
Having continued as negotiator with the Mōri, Masakatsu by around this year became the most respected senior retainer in Hideyoshi's household. He was given a residence right next to Osaka Castle and went to the castle every day as a close aide. Meanwhile he had already left the management of his Tatsuno lands to his son Iemasa and handed over headship of the house.
Before the Shikoku campaign, Hideyoshi told Masakatsu he would grant him the whole province of Awa upon victory. But Masakatsu declined, saying he was already old and retired and wished to serve at Hideyoshi's side in Osaka, and asked that it be given to his son Iemasa instead. Thus Awa went to Iemasa, marking the beginning of the Tokushima domain.
This year he fell ill and recuperated in Kyoto, recovered for a time and returned to Osaka, but soon died at his Osaka residence. The famous story that he met Hideyoshi as a young man on a bridge is considered a creation of Edo-period popular literature. The real Masakatsu was a chief vassal of Hideyoshi who excelled at negotiation and winning people over.
Saitō DōsanOda NobunagaToyotomi HideyoshiKuroda Yoshitaka (Kanbei)Kuroda Nagamasa
Sen no RikyūShibata KatsuieMiyoshi NagayoshiTakigawa KazumasuSakai TadatsuguAkechi MitsuhideRyuzoji TakanobuUesugi Kenshin
People of the Sengoku/Azuchi-Momoyama period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.