Editing Tokugawa Ieyasu (section)

=== Suruga campaign against Takeda clan ===
{{Main|Battle of Mikatagahara|Battle of Nagashino}}
In October 1571, Takeda Shingen broke the alliance with the Oda-Tokugawa forces and allied with the [[Late Hōjō clan|Odawara Hōjō clan]]. He decided to make a drive for Kyoto at the urging of the shōgun [[Ashikaga Yoshiaki]], starting by invading Tokugawa lands in Tōtōmi. Takeda Shingen's first objectives in his campaign against Ieyasu were [[Nishikawa Castle]], [[Yoshida Castle (Mikawa Province)|Yoshida Castle]] and [[Futamata Castle]]. 

In 1572, after [[Siege of Futamata|besieging Futamata]], Shingen would press on past Futamata towards the major Tokugawa home castle at [[Hamamatsu]]. Ieyasu asked for help from Nobunaga, who sent him some 3,000 troops. Early in 1573, the two armies met at the [[Battle of Mikatagahara]], north of Hamamatsu. The considerably larger Takeda army, under the expert direction of Shingen, overwhelmed Ieyasu's troops and caused heavy casualties. Despite his initial reluctance, Ieyasu was convinced by his generals to retreat.<ref name="Cassell">{{cite book|last1=Turnbull|first1=Stephen|title=The Samurai Sourcebook|date=2000|publisher=Cassell & Co|location=London|isbn=1854095234|pages=222–223}}</ref><ref name="Arms"/> 

The battle was a major defeat, but in the interest of maintaining the appearance of a dignified withdrawal, Ieyasu brazenly ordered the men in his castle to light torches, sound drums, and leave the gates open, to properly receive the returning warriors. To the surprise and relief of the Tokugawa army, this spectacle made the Takeda generals suspicious that they were being led into a trap, so they did not besiege the castle and instead made camp for the night.<ref name="Cassell"/> This error allowed a band of Tokugawa soldiers to raid the camp in the ensuing hours, further upsetting the already disoriented Takeda army, and ultimately resulting in Shingen's decision to call off the offensive altogether. Takeda Shingen would not get another chance to advance on Hamamatsu, much less Kyoto, since he died from unknown causes shortly after the [[siege of Noda Castle]] later that same year.<ref name="sam"/>{{rp|153–156}}

In 1574, Shingen was succeeded by his son [[Takeda Katsuyori]] and the conflict continued as the Tokugawa forces under Honda Tadakatsu and Sakakibara Yasumasa seized many of the Takeda clan's castles,<ref name="Nagashino1573;TadakatsuYasumasa">{{cite book |author1=Murata Shuzo |author2=Hattori Hideo |title=都道府県別日本の中世城館調査報告書集成 |trans-title=Collection of Japanese medieval castle survey reports by prefecture |date=2000 |publisher=東洋書林 |isbn=4887214324 |page=418 |url=https://ci.nii.ac.jp/ncid/BA49003233 |access-date=22 May 2024 |language=Ja}}</ref><ref>{{cite book |author1=Shin Jinbutsu Ōraisha |title=歴史読本, Volume 52, Issue 3 |trans-title=History Reader, Volume 52, Masalah |date=2007 |publisher=新人物往来社 |page=92 |url=https://books.google.com/books?id=v1ozAQAAIAAJ |access-date=22 May 2024 |language=Ja}}</ref> including Komyo Castle.<ref name="Research establishment">{{cite book |author1=煎本 増夫 |title=幕藩体制成立史の研究 |trans-title=Research on the history of the establishment of the Shogunate system |date=1979 |publisher=雄山閣出版 |page=94 |url=https://bookmeter.com/books/1502589 |access-date=15 May 2024 |language=Ja}}</ref><ref name="Research of Fudai">{{cite book |author1=Naito Family Documents Study Group |title=譜代藩の研究 : 譜代内藤藩の藩政と藩領 |trans-title=Research on the Fudai domain: the government and domain of the Fudai Naito domain |date=1972 |publisher=Meiji University |page=44 |url=https://ndlsearch.ndl.go.jp/books/R100000002-I000001212352 |access-date=15 May 2024 |language=Ja}}</ref> At some point, Ieyasu tried to capture Inui Castle in Tōtōmi Province, but strong resistance from its garrison commander, Amano Kagehira, forced Ieyasu to abort the siege. During their retreat, Kagehira launched a counterattack to pursue Ieyasu, but this was repelled by [[Mizuno Tadashige]] and Torii Mototada, who led the rearguard.<ref>{{cite book|last=Hotta|first=Masaatsu|date=1923| title =寛政重脩諸家譜. 第2輯|publisher =國民圖書|language=Ja |page=823}}</ref>

In April 1575, Ōga Yashirō, a deputy governor of over 20 villages in Oku district of Mikawa under Matsudaira Nobuyasu,<ref name="Hamada Koichiro; Yashiro incident" /> was arrested by [[Ōkubo Tadayo]] and paraded around [[Hamamatsu Castle]]. According to the investigation, Yashirō was implicated in allegations of colluding with Takeda Katsuyori to betray Ieyasu and invade the Tokugawa clan's territory. According to a letter, Yashiro had teamed up with Takeda Katsuyori of Kai to seize Okazaki Castle. However, one of Yashiro's colleagues, Yamada Hachizō, betrayed Yashiro and passed this information to Nobuyasu. Meanwhile, Ieyasu himself also learned about Yashirō's further crimes of corruption in governance through a vassal's report.<ref name="Hamada Koichiro; Yashiro incident">{{cite web |author1=Hamada Kōichirō (濱田浩一郎) |title=「どうする家康」『徳川実紀』が描く大岡弥四郎事件 岡崎クーデターはなぜ失敗したのか？ |trans-title="What would you do, Ieyasu?" The Ōga Yashirō Incident as described in the Tokugawa Jikki: Why did the Okazaki Coup fail? |url=https://sengoku-his.com/694 |website=Rekishijin |publisher=Abc Arc, inc. |access-date=9 June 2024 |language=Ja |date=2023}}</ref> Yashirō was then executed by being mutilated alive with a saw, while Tadayo crucified his wife and children.<ref name="OgaYashiro; Watanabe Daimon1">{{cite web |author1=Watanabe Daimon |title=残酷すぎて放映できなかった、大岡弥四郎のあまりにむごたらしい最期 |url=https://news.yahoo.co.jp/expert/articles/df6862aa19e2d4a45354f63f4cd6a4c22a740cfc |website=yahoo.co.jp/expert/articles/ |publisher=渡邊大門 無断転載を禁じます。 © LY Corporation |access-date=4 June 2024 |language=Ja}}</ref> 

In June, during Takeda Katsuyori's raid on Mikawa Province when he [[Siege of Yoshida Castle|attacked Yoshida Castle]] and [[Battle of Nagashino|besieged Nagashino Castle]], Ieyasu appealed to Nobunaga for help; Nobunaga came personally with 30,000 men. The Oda-Tokugawa forces 38,000 strong won a great victory and successfully defended Nagashino Castle. Though the Takeda forces had been destroyed, Katsuyori survived the battle and retreated to [[Kai Province]].<ref>{{Cite book|last=Turnbull|first=Stephen|url=https://books.google.com/books?id=savvCwAAQBAJ&q=temple+on+the+road+back+towards+kai|title=Nagashino 1575: Slaughter at the barricades|date=2012|publisher=Bloomsbury Publishing|isbn=978-1-78200-229-1|pages=79|language=en}}</ref> For the next seven years, Ieyasu and Katsuyori fought a series of small battles through which Ieyasu's troops managed to wrest control of [[Suruga Province]] from the Takeda clan.