Hosokawa Fujitaka's eldest son, Tadaoki fought his first battle at the age of 15 in the service of Oda Nobunaga. Along with his father he was given the province of Tango in 1580, soon afterwards married the daughter of Akechi Mitsuhide, noted Oda general and a friend of Fujitaka. In 1582 Akechi rebelled and after Nobunaga was killed, he turned to the Hosokawa for help. Tadaoki replied by preparing to send his wife back to the Akechi and both he and Fujitaka refused to provide their erstwhile comrade with any assistance. After Hideyoshi defeated Mitsuhide, he convinced Tadaoki to take his wife back.
Tadaoki was present on Hideyoshi's side in the Komaki Campaign (1583) and the Odawara Campaign (1590), where he took part in the siege of Nirayama (Izu province) and later joined the main army outside Odawara. During the 1590's he became friends with Tokugawa Ieyasu (who had lent him money to assist in some debts owed Toyotomi Hidetsugu) and in 1600 sided with him against Ishida Mitsunari. In July Ishida had attempted to gain some leverage over those leaning towards Ieyasu by taking as hostages all those whose families were in Ôsaka Castle. This happened to include Tadaoki's wife - who was by now a Christian, baptized 'Gracia'. To avoid capture, Gracia ordered a servant to kill her and set fire to their quarters. While there is little reason to believe that Hosokawa was emotionally scarred by the incident, it was considered an appalling act of trickery, and served to drive Tadaoki - among others - into Ieyasu's camp.
At the Battle of Sekigahara (21 October 1600) Tadaoki commanded 5,000 men in the Tokugawa vanguard and clashed with the forces of Shima Sakon. He was awarded a fief in Buzen (Kokura, 370,000 koku) and went on to serve at the Ôsaka Campaigns (1614,1615). He was succeeded by Tadatoshi (1586-1641), an ardent enemy of Christianity and present at the Siege of Shimabara (1632). In 1632 he received a huge fief in Higo (Kumamoto han, 540,000 koku).
A noted warrior and something of a scholar (though far less so then his father), Tadaoki also seems to have been rather ill-tempered - clashing with his father on more then one occasion and, according to his wife, killing more then one servant girl.
- Initial text from Samurai-Archives.com FWSeal & CEWest, 2005