Editing Tokugawa Ieyasu (section)

=== Becoming a vassal of the Toyotomi Regency ===
The conflict with Hideyoshi was long, and lasted until Nobukatsu decided to surrender to Hideyoshi. With this, Ieyasu lost his motivation to further oppose Hideyoshi and decided to also submit.<ref name=Sansom />{{sfn|Turnbull|1998|p=235}} After peace negotiations between Tokugawa Ieyasu and Toyotomi Hideyoshi in the aftermath of the [[Battle of Komaki and Nagakute]], Naomasa, Tadakatsu, and Yasumasa gained fame in Kyoto. The following month, the three of them were joined by Tadatsugu Sakai while accompanying Ieyasu on a trip to Kyoto, where the four of them became famous.<ref name="徳川四天王">{{cite book |author1=Tetsuo Nakamura |author2=Kazuo Murayama |title=徳川四天王: 精強家康軍団奮闘譜 歴史群像シリーズ22号 |date=1991 |publisher=学研プラス |isbn=4051053679 |pages=111, 125 }}</ref>

However, on November 13, 1585, [[Ishikawa Kazumasa]] defected from Ieyasu to Hideyoshi.{{sfn|Tanaka|2007|p=14}} Ogasawara Sadayoshi, who also defected and followed Kazumasa, led over 3,000 troops to attack Takato. In Takato Castle there were only 40 cavalrymen and 360 soldiers other than the elderly Hoshina Masatoshi, but Masatoshi himself took command and defeated the Ogasawara forces in open battle. This prevented the collapse of Tokugawa rule in Shinano and Ieyasu awarded Masanao with the sword of Tsunehisa on December 24 in recognition of his military achievements.{{sfn|Hirayama|2011|p=179-182}} 

These incidents caused Ieyasu to undertake massive reforms of the Tokugawa clan governmental structure by incorporating more Takeda clan vassals into his administrations, both civil and military. At first, Ieyasu ordered Torii Mototada, who served as the county magistrate of Kai, to collect military laws, weapons, and military equipment from the time of Takeda Shingen and bring them to Hamamatsu Castle in Hamamatsu City, Shizuoka Prefecture. Later, he appointed two former Takeda vassals, Naruse Masakazu and Okabe Masatsuna, as magistrates under authority of Ii Naomasa and Honda Tadakatsu. He ordered all former Takeda vassals who served him to impart any military doctrines and structures they knew from their service to the Takeda clan.,<ref name="Shogun and Samurai Tales of Nobunaga, Hideyoshi, and Ieyasu">{{cite book |author1=Okanoya Shigezane |translator=Andrew and Yoshiko Dykstra |title=Shogun and Samurai Tales of Nobunaga, Hideyoshi, and Ieyasu |date=2007 |publisher=University of Hawaiʻi; Japanese Literature Translations by Yoshiko K. Dykstra |location=Mānoa |page=147 |url=https://scholarspace.manoa.hawaii.edu/server/api/core/bitstreams/0d434090-1065-4bc9-ab1f-31611d094ba2/content |access-date=2 June 2024 |language=En}}</ref> He ordered three of his prime generals, Ii Naomasa, Honda Tadakatsu, and Sakakibara Yasumasa, to serve as the supreme commanders of these new military regiments.<ref>{{cite web |author1=Watanabe Daimon |title=家臣が出奔するというピンチをチャンスに変えた、徳川家康の先見性とは |publisher=渡邊大門 無断転載を禁じます。 © LY Corporation |website=yahoo.co.jp/expert/articles/ |url=https://news.yahoo.co.jp/expert/articles/a826d1080466b78200a81bb25683c64862298924 |access-date=2 June 2024 |language=Ja}}</ref> The same year, Hideyoshi forced his younger sister [[Asahi no kata]] to divorce her husband, who then committed suicide, and sent her to Ieyasu with the offer of marrying her.{{Sfn|Fujino |1990|p=59}}

In 1586, in response to Ishikawa Kazumasa's defection from the Tokugawa clan, former Takeda clan vassals from Kai and Shinano province, including Yonekura Tadatsugu, sought to reaffirm their loyalty to Ieyasu by presenting their family members as hostages.<ref>{{harvtxt|Kazuhiro Marushima (丸島和洋)|2015|p=706}}</ref>

Later the same year, Hideyoshi sent [[Ōmandokoro|his own mother]] as a hostage to Ieyasu. If Ieyasu continued to refuse to go to Kyoto after such a gesture, it would give Hideyoshi a just cause for war. Ieyasu finally decided to become Hideyoshi's vassal.<ref>{{cite web|url=https://hamamatsu-daisuki.net/ieyasu/person/relation/|title=1586年に秀吉の母・大政所を人質として岡崎に迎えた後に上洛。大坂城で秀吉に臣下の礼をとり、秀吉の家来となりました。|publisher=Hamamatsu & Lake Hamana Tourism Bureau|access-date=June 7, 2024}}</ref>